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Friday, April 11, 2025

Linguistics

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Linguistics

Linguistics
is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), morphology (structure of words), phonetics (speech sounds and equivalent gestures in sign languages), phonology (the abstract sound system of a particular language, and analogous systems of sign languages), and pragmatics (how the context of use contributes to meaning). Subdisciplines such as biolinguistics (the study of the biological variables and evolution of language) and psycholinguistics (the study of psychological factors in human language) bridge many of these divisions.

Linguistics encompasses many branches and subfields that span both theoretical and practical applications. Theoretical linguistics is concerned with understanding the universal and fundamental nature of language and developing a general theoretical framework for describing it. Applied linguistics seeks to utilize the scientific findings of the study of language for practical purposes, such as developing methods of improving language education and literacy.

Linguistic features may be studied through a variety of perspectives: synchronically (by describing the structure of a language at a specific point in time) or diachronically (through the historical development of a language over a period of time), in monolinguals or in multilinguals, among children or among adults, in terms of how it is being learnt or how it was acquired, as abstract objects or as cognitive structures, through written texts or through oral elicitation, and finally through mechanical data collection or practical fieldwork.

Linguistics emerged from the field of philology, of which some branches are more qualitative and holistic in approach. Today, philology and linguistics are variably described as related fields, subdisciplines, or separate fields of language study but, by and large, linguistics can be seen as an umbrella term. Linguistics is also related to the philosophy of language, stylistics, rhetoric, semiotics, lexicography, and translation.

Major subdisciplines

Swiss linguist Ferdinand de Saussure is regarded as the creator of semiotics

Historical linguistics

Historical linguistics is the study of how language changes over history, particularly with regard to a specific language or a group of languages. Western trends in historical linguistics date back to roughly the late 18th century, when the discipline grew out of philology, the study of ancient texts and oral traditions.

Historical linguistics emerged as one of the first few sub-disciplines in the field, and was most widely practised during the late 19th century. Despite a shift in focus in the 20th century towards formalism and generative grammar, which studies the universal properties of language, historical research today still remains a significant field of linguistic inquiry. Subfields of the discipline include language change and grammaticalization.

Historical linguistics studies language change either diachronically (through a comparison of different time periods in the past and present) or in a synchronic manner (by observing developments between different variations that exist within the current linguistic stage of a language).

At first, historical linguistics was the cornerstone of comparative linguistics, which involves a study of the relationship between different languages. At that time, scholars of historical linguistics were only concerned with creating different categories of language families, and reconstructing prehistoric proto-languages by using both the comparative method and the method of internal reconstruction. Internal reconstruction is the method by which an element that contains a certain meaning is re-used in different contexts or environments where there is a variation in either sound or analogy.

The reason for this had been to describe well-known Indo-European languages, many of which had detailed documentation and long written histories. Scholars of historical linguistics also studied Uralic languages, another European language family for which very little written material existed back then. After that, there also followed significant work on the corpora of other languages, such as the Austronesian languages and the Native American language families.

In historical work, the uniformitarian principle is generally the underlying working hypothesis, occasionally also clearly expressed. The principle was expressed early by William Dwight Whitney, who considered it imperative, a "must", of historical linguistics to "look to find the same principle operative also in the very outset of that [language] history."

The above approach of comparativism in linguistics is now, however, only a small part of the much broader discipline called historical linguistics. The comparative study of specific Indo-European languages is considered a highly specialized field today, while comparative research is carried out over the subsequent internal developments in a language: in particular, over the development of modern standard varieties of languages, and over the development of a language from its standardized form to its varieties.

For instance, some scholars also tried to establish super-families, linking, for example, Indo-European, Uralic, and other language families to a hypothetical Nostratic language group. While these attempts are still not widely accepted as credible methods, they provide necessary information to establish relatedness in language change. This is generally hard to find for events long ago, due to the occurrence of chance word resemblances and variations between language groups. A limit of around 10,000 years is often assumed for the functional purpose of conducting research. It is also hard to date various proto-languages. Even though several methods are available, these languages can be dated only approximately.

In modern historical linguistics, we examine how languages change over time, focusing on the relationships between dialects within a specific period. This includes studying morphological, syntactical, and phonetic shifts. Connections between dialects in the past and present are also explored.

Syntax

Syntax is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, constituency, agreement, the nature of crosslinguistic variation, and the relationship between form and meaning. There are numerous approaches to syntax that differ in their central assumptions and goals.

Morphology

Morphology is the study of words, including the principles by which they are formed, and how they relate to one another within a language. Most approaches to morphology investigate the structure of words in terms of morphemes, which are the smallest units in a language with some independent meaning. Morphemes include roots that can exist as words by themselves, but also categories such as affixes that can only appear as part of a larger word. For example, in English the root catch and the suffix -ing are both morphemes; catch may appear as its own word, or it may be combined with -ing to form the new word catching. Morphology also analyzes how words behave as parts of speech, and how they may be inflected to express grammatical categories including number, tense, and aspect. Concepts such as productivity are concerned with how speakers create words in specific contexts, which evolves over the history of a language.

The discipline that deals specifically with the sound changes occurring within morphemes is morphophonology.

Semantics and pragmatics

Semantics and pragmatics are branches of linguistics concerned with meaning. These subfields have traditionally been divided according to aspects of meaning: "semantics" refers to grammatical and lexical meanings, while "pragmatics" is concerned with meaning in context. Within linguistics, the subfield of formal semantics studies the denotations of sentences and how they are composed from the meanings of their constituent expressions. Formal semantics draws heavily on philosophy of language and uses formal tools from logic and computer science. On the other hand, cognitive semantics explains linguistic meaning via aspects of general cognition, drawing on ideas from cognitive science such as prototype theory.

Pragmatics focuses on phenomena such as speech acts, implicature, and talk in interaction. Unlike semantics, which examines meaning that is conventional or "coded" in a given language, pragmatics studies how the transmission of meaning depends not only on the structural and linguistic knowledge (grammar, lexicon, etc.) of the speaker and listener, but also on the context of the utterance, any pre-existing knowledge about those involved, the inferred intent of the speaker, and other factors.

Phonetics and phonology

Phonetics and phonology are branches of linguistics concerned with sounds (or the equivalent aspects of sign languages). Phonetics is largely concerned with the physical aspects of sounds such as their articulation, acoustics, production, and perception. Phonology is concerned with the linguistic abstractions and categorizations of sounds, and it tells us what sounds are in a language, how they do and can combine into words, and explains why certain phonetic features are important to identifying a word.

Typology

Linguistic typology (or language typology) is a field of linguistics that studies and classifies languages according to their structural features to allow their comparison. Its aim is to describe and explain the structural diversity and the common properties of the world's languages. Its subdisciplines include, but are not limited to phonological typology, which deals with sound features; syntactic typology, which deals with word order and form; lexical typology, which deals with language vocabulary; and theoretical typology, which aims to explain the universal tendencies.

Structures

Linguistic structures are pairings of meaning and form. Any particular pairing of meaning and form is a Saussurean linguistic sign. For instance, the meaning "cat" is represented worldwide with a wide variety of different sound patterns (in oral languages), movements of the hands and face (in sign languages), and written symbols (in written languages). Linguistic patterns have proven their importance for the knowledge engineering field especially with the ever-increasing amount of available data.

Linguists focusing on structure attempt to understand the rules regarding language use that native speakers know (not always consciously). All linguistic structures can be broken down into component parts that are combined according to (sub)conscious rules, over multiple levels of analysis. For instance, consider the structure of the word "tenth" on two different levels of analysis. On the level of internal word structure (known as morphology), the word "tenth" is made up of one linguistic form indicating a number and another form indicating ordinality. The rule governing the combination of these forms ensures that the ordinality marker "th" follows the number "ten." On the level of sound structure (known as phonology), structural analysis shows that the "n" sound in "tenth" is made differently from the "n" sound in "ten" spoken alone. Although most speakers of English are consciously aware of the rules governing internal structure of the word pieces of "tenth", they are less often aware of the rule governing its sound structure. Linguists focused on structure find and analyze rules such as these, which govern how native speakers use language.

Grammar

Grammar is a system of rules which governs the production and use of utterances in a given language. These rules apply to sound as well as meaning, and include componential subsets of rules, such as those pertaining to phonology (the organization of phonetic sound systems), morphology (the formation and composition of words), and syntax (the formation and composition of phrases and sentences). Modern frameworks that deal with the principles of grammar include structural and functional linguistics, and generative linguistics.

Sub-fields that focus on a grammatical study of language include the following:

  • Phonetics, the study of the physical properties of speech sound production and perception, and delves into their acoustic and articulatory properties
  • Phonology, the study of sounds as abstract elements in the speaker's mind that distinguish meaning (phonemes)
  • Morphology, the study of morphemes, or the internal structures of words and how they can be modified
  • Syntax, the study of how words combine to form grammatical phrases and sentences
  • Semantics, the study of lexical and grammatical aspects of meaning
  • Pragmatics, the study of how utterances are used in communicative acts, and the role played by situational context and non-linguistic knowledge in the transmission of meaning
  • Discourse analysis, the analysis of language use in texts (spoken, written, or signed)
  • Stylistics, the study of linguistic factors (rhetoric, diction, stress) that place a discourse in context
  • Semiotics, the study of signs and sign processes (semiosis), indication, designation, likeness, analogy, metaphor, symbolism, signification, and communication

Discourse

Discourse is language as social practice (Baynham, 1995) and is a multilayered concept. As a social practice, discourse embodies different ideologies through written and spoken texts. Discourse analysis can examine or expose these ideologies. Discourse not only influences genre, which is selected based on specific contexts but also, at a micro level, shapes language as text (spoken or written) down to the phonological and lexico-grammatical levels. Grammar and discourse are linked as parts of a system. A particular discourse becomes a language variety when it is used in this way for a particular purpose, and is referred to as a register. There may be certain lexical additions (new words) that are brought into play because of the expertise of the community of people within a certain domain of specialization. Thus, registers and discourses distinguish themselves not only through specialized vocabulary but also, in some cases, through distinct stylistic choices. People in the medical fraternity, for example, may use some medical terminology in their communication that is specialized to the field of medicine. This is often referred to as being part of the "medical discourse", and so on.

Lexicon

The lexicon is a catalogue of words and terms that are stored in a speaker's mind. The lexicon consists of words and bound morphemes, which are parts of words that can not stand alone, like affixes. In some analyses, compound words and certain classes of idiomatic expressions and other collocations are also considered to be part of the lexicon. Dictionaries represent attempts at listing, in alphabetical order, the lexicon of a given language; usually, however, bound morphemes are not included. Lexicography, closely linked with the domain of semantics, is the science of mapping the words into an encyclopedia or a dictionary. The creation and addition of new words (into the lexicon) is called coining or neologization, and the new words are called neologisms.

It is often believed that a speaker's capacity for language lies in the quantity of words stored in the lexicon. However, this is often considered a myth by linguists. The capacity for the use of language is considered by many linguists to lie primarily in the domain of grammar, and to be linked with competence, rather than with the growth of vocabulary. Even a very small lexicon is theoretically capable of producing an infinite number of sentences.

Vocabulary size is relevant as a measure of comprehension. There is general consensus that reading comprehension of a written text in English requires 98% coverage, meaning that the person understands 98% of the words in the text. The question of how much vocabulary is needed is therefore related to which texts or conversations need to be understood. A common estimate is 6-7,000 word families to understand a wide range of conversations and 8-9,000 word families to be able to read a wide range of written texts.

Style

Stylistics also involves the study of written, signed, or spoken discourse through varying speech communities, genres, and editorial or narrative formats in the mass media. It involves the study and interpretation of texts for aspects of their linguistic and tonal style. Stylistic analysis entails the analysis of description of particular dialects and registers used by speech communities. Stylistic features include rhetoric, diction, stress, satire, irony, dialogue, and other forms of phonetic variations. Stylistic analysis can also include the study of language in canonical works of literature, popular fiction, news, advertisements, and other forms of communication in popular culture as well. It is usually seen as a variation in communication that changes from speaker to speaker and community to community. In short, Stylistics is the interpretation of text.

In the 1960s, Jacques Derrida, for instance, further distinguished between speech and writing, by proposing that written language be studied as a linguistic medium of communication in itself. Palaeography is therefore the discipline that studies the evolution of written scripts (as signs and symbols) in language. The formal study of language also led to the growth of fields like psycholinguistics, which explores the representation and function of language in the mind; neurolinguistics, which studies language processing in the brain; biolinguistics, which studies the biology and evolution of language; and language acquisition, which investigates how children and adults acquire the knowledge of one or more languages.

Approaches

Humanistic

The fundamental principle of humanistic linguistics, especially rational and logical grammar, is that language is an invention created by people. A semiotic tradition of linguistic research considers language a sign system which arises from the interaction of meaning and form. The organization of linguistic levels is considered computational. Linguistics is essentially seen as relating to social and cultural studies because different languages are shaped in social interaction by the speech community. Frameworks representing the humanistic view of language include structural linguistics, among others.

Structural analysis means dissecting each linguistic level: phonetic, morphological, syntactic, and discourse, to the smallest units. These are collected into inventories (e.g. phoneme, morpheme, lexical classes, phrase types) to study their interconnectedness within a hierarchy of structures and layers. Functional analysis adds to structural analysis the assignment of semantic and other functional roles that each unit may have. For example, a noun phrase may function as the subject or object of the sentence; or the agent or patient.

Functional linguistics, or functional grammar, is a branch of structural linguistics. In the humanistic reference, the terms structuralism and functionalism are related to their meaning in other human sciences. The difference between formal and functional structuralism lies in the way that the two approaches explain why languages have the properties they have. Functional explanation entails the idea that language is a tool for communication, or that communication is the primary function of language. Linguistic forms are consequently explained by an appeal to their functional value, or usefulness. Other structuralist approaches take the perspective that form follows from the inner mechanisms of the bilateral and multilayered language system.

Biological

Approaches such as cognitive linguistics and generative grammar study linguistic cognition with a view towards uncovering the biological underpinnings of language. In Generative Grammar, these underpinning are understood as including innate domain-specific grammatical knowledge. Thus, one of the central concerns of the approach is to discover what aspects of linguistic knowledge are innate and which are not.

Cognitive linguistics, in contrast, rejects the notion of innate grammar, and studies how the human mind creates linguistic constructions from event schemas, and the impact of cognitive constraints and biases on human language. In cognitive linguistics, language is approached via the senses.

A closely related approach is evolutionary linguistics which includes the study of linguistic units as cultural replicators. It is possible to study how language replicates and adapts to the mind of the individual or the speech community. Construction grammar is a framework which applies the meme concept to the study of syntax.

The generative versus evolutionary approach are sometimes called formalism and functionalism, respectively. This reference is however different from the use of the terms in human sciences.

Methodology

Modern linguistics is primarily descriptive. Linguists describe and explain features of language without making subjective judgments on whether a particular feature or usage is "good" or "bad". This is analogous to practice in other sciences: a zoologist studies the animal kingdom without making subjective judgments on whether a particular species is "better" or "worse" than another.

Prescription, on the other hand, is an attempt to promote particular linguistic usages over others, often favoring a particular dialect or "acrolect". This may have the aim of establishing a linguistic standard, which can aid communication over large geographical areas. It may also, however, be an attempt by speakers of one language or dialect to exert influence over speakers of other languages or dialects (see Linguistic imperialism). An extreme version of prescriptivism can be found among censors, who attempt to eradicate words and structures that they consider to be destructive to society. Prescription, however, may be practised appropriately in language instruction, like in ELT, where certain fundamental grammatical rules and lexical items need to be introduced to a second-language speaker who is attempting to acquire the language.

Sources

Most contemporary linguists work under the assumption that spoken data and signed data are more fundamental than written data. This is because

  • Speech appears to be universal to all human beings capable of producing and perceiving it, while there have been many cultures and speech communities that lack written communication;
  • Features appear in speech which are not always recorded in writing, including phonological rules, sound changes, and speech errors;
  • All natural writing systems reflect a spoken language (or potentially a signed one), even with pictographic scripts like Dongba writing Naxi homophones with the same pictogram, and text in writing systems used for two languages changing to fit the spoken language being recorded;
  • Speech evolved before human beings invented writing;
  • Individuals learn to speak and process spoken language more easily and earlier than they do with writing.

Nonetheless, linguists agree that the study of written language can be worthwhile and valuable. For research that relies on corpus linguistics and computational linguistics, written language is often much more convenient for processing large amounts of linguistic data. Large corpora of spoken language are difficult to create and hard to find, and are typically transcribed and written. In addition, linguists have turned to text-based discourse occurring in various formats of computer-mediated communication as a viable site for linguistic inquiry.

The study of writing systems themselves, graphemics, is, in any case, considered a branch of linguistics.

Analysis

Before the 20th century, linguists analysed language on a diachronic plane, which was historical in focus. This meant that they would compare linguistic features and try to analyse language from the point of view of how it had changed between then and later. However, with the rise of Saussurean linguistics in the 20th century, the focus shifted to a more synchronic approach, where the study was geared towards analysis and comparison between different language variations, which existed at the same given point of time.

At another level, the syntagmatic plane of linguistic analysis entails the comparison between the way words are sequenced, within the syntax of a sentence. For example, the article "the" is followed by a noun, because of the syntagmatic relation between the words. The paradigmatic plane, on the other hand, focuses on an analysis that is based on the paradigms or concepts that are embedded in a given text. In this case, words of the same type or class may be replaced in the text with each other to achieve the same conceptual understanding.

History

The earliest activities in the description of language have been attributed to the 6th-century-BC Indian grammarian Pāṇini who wrote a formal description of the Sanskrit language in his Aṣṭādhyāyī. Today, modern-day theories on grammar employ many of the principles that were laid down then.

Nomenclature

Before the 20th century, the term philology, first attested in 1716, was commonly used to refer to the study of language, which was then predominantly historical in focus. Since Ferdinand de Saussure's insistence on the importance of synchronic analysis, however, this focus has shifted and the term philology is now generally used for the "study of a language's grammar, history, and literary tradition", especially in the United States (where philology has never been very popularly considered as the "science of language").

Although the term linguist in the sense of "a student of language" dates from 1641, the term linguistics is first attested in 1847. It is now the usual term in English for the scientific study of language, though linguistic science is sometimes used.

Linguistics is a multi-disciplinary field of research that combines tools from natural sciences, social sciences, formal sciences, and the humanities. Many linguists, such as David Crystal, conceptualize the field as being primarily scientific. The term linguist applies to someone who studies language or is a researcher within the field, or to someone who uses the tools of the discipline to describe and analyse specific languages.

Early grammarians

An early formal study of language was in India with Pāṇini, the 6th century BC grammarian who formulated 3,959 rules of Sanskrit morphology. Pāṇini's systematic classification of the sounds of Sanskrit into consonants and vowels, and word classes, such as nouns and verbs, was the first known instance of its kind. In the Middle East, Sibawayh, a Persian, made a detailed description of Arabic in AD 760 in his monumental work, Al-kitab fii an-naħw (الكتاب في النحو, The Book on Grammar), the first known author to distinguish between sounds and phonemes (sounds as units of a linguistic system). Western interest in the study of languages began somewhat later than in the East, but the grammarians of the classical languages did not use the same methods or reach the same conclusions as their contemporaries in the Indic world. Early interest in language in the West was a part of philosophy, not of grammatical description. The first insights into semantic theory were made by Plato in his Cratylus dialogue, where he argues that words denote concepts that are eternal and exist in the world of ideas. This work is the first to use the word etymology to describe the history of a word's meaning. Around 280 BC, one of Alexander the Great's successors founded a university (see Musaeum) in Alexandria, where a school of philologists studied the ancient texts in Greek, and taught Greek to speakers of other languages. While this school was the first to use the word "grammar" in its modern sense, Plato had used the word in its original meaning as "téchnē grammatikḗ" (Τέχνη Γραμματική), the "art of writing", which is also the title of one of the most important works of the Alexandrine school by Dionysius Thrax. Throughout the Middle Ages, the study of language was subsumed under the topic of philology, the study of ancient languages and texts, practised by such educators as Roger Ascham, Wolfgang Ratke, and John Amos Comenius.

Comparative philology

In the 18th century, the first use of the comparative method by William Jones sparked the rise of comparative linguistics. Bloomfield attributes "the first great scientific linguistic work of the world" to Jacob Grimm, who wrote Deutsche Grammatik. It was soon followed by other authors writing similar comparative studies on other language groups of Europe. The study of language was broadened from Indo-European to language in general by Wilhelm von Humboldt, of whom Bloomfield asserts:

This study received its foundation at the hands of the Prussian statesman and scholar Wilhelm von Humboldt (1767–1835), especially in the first volume of his work on Kavi, the literary language of Java, entitled Über die Verschiedenheit des menschlichen Sprachbaues und ihren Einfluß auf die geistige Entwickelung des Menschengeschlechts (On the Variety of the Structure of Human Language and its Influence upon the Mental Development of the Human Race).

20th-century developments

There was a shift of focus from historical and comparative linguistics to synchronic analysis in early 20th century. Structural analysis was improved by Leonard Bloomfield, Louis Hjelmslev; and Zellig Harris who also developed methods of discourse analysis. Functional analysis was developed by the Prague linguistic circle and André Martinet. As sound recording devices became commonplace in the 1960s, dialectal recordings were made and archived, and the audio-lingual method provided a technological solution to foreign language learning. The 1960s also saw a new rise of comparative linguistics: the study of language universals in linguistic typology. Towards the end of the century the field of linguistics became divided into further areas of interest with the advent of language technology and digitalized corpora.

Areas of research

Sociolinguistics

Sociolinguistics is the study of how language is shaped by social factors. This sub-discipline focuses on the synchronic approach of linguistics, and looks at how a language in general, or a set of languages, display variation and varieties at a given point in time. The study of language variation and the different varieties of language through dialects, registers, and idiolects can be tackled through a study of style, as well as through analysis of discourse. Sociolinguists research both style and discourse in language, as well as the theoretical factors that are at play between language and society.

Developmental linguistics

Developmental linguistics is the study of the development of linguistic ability in individuals, particularly the acquisition of language in childhood. Some of the questions that developmental linguistics looks into are how children acquire different languages, how adults can acquire a second language, and what the process of language acquisition is.

Neurolinguistics

Neurolinguistics is the study of the structures in the human brain that underlie grammar and communication. Researchers are drawn to the field from a variety of backgrounds, bringing along a variety of experimental techniques as well as widely varying theoretical perspectives. Much work in neurolinguistics is informed by models in psycholinguistics and theoretical linguistics, and is focused on investigating how the brain can implement the processes that theoretical and psycholinguistics propose are necessary in producing and comprehending language. Neurolinguists study the physiological mechanisms by which the brain processes information related to language, and evaluate linguistic and psycholinguistic theories, using aphasiology, brain imaging, electrophysiology, and computer modelling. Amongst the structures of the brain involved in the mechanisms of neurolinguistics, the cerebellum which contains the highest numbers of neurons has a major role in terms of predictions required to produce language.

Applied linguistics

Linguists are largely concerned with finding and describing the generalities and varieties both within particular languages and among all languages. Applied linguistics takes the results of those findings and "applies" them to other areas. Linguistic research is commonly applied to areas such as language education, lexicography, translation, language planning, which involves governmental policy implementation related to language use, and natural language processing. "Applied linguistics" has been argued to be something of a misnomer. Applied linguists actually focus on making sense of and engineering solutions for real-world linguistic problems, and not literally "applying" existing technical knowledge from linguistics. Moreover, they commonly apply technical knowledge from multiple sources, such as sociology (e.g., conversation analysis) and anthropology. (Constructed language fits under Applied linguistics.)

Today, computers are widely used in many areas of applied linguistics. Speech synthesis and speech recognition use phonetic and phonemic knowledge to provide voice interfaces to computers. Applications of computational linguistics in machine translation, computer-assisted translation, and natural language processing are areas of applied linguistics that have come to the forefront. Their influence has had an effect on theories of syntax and semantics, as modelling syntactic and semantic theories on computers constraints.

Linguistic analysis is a sub-discipline of applied linguistics used by many governments to verify the claimed nationality of people seeking asylum who do not hold the necessary documentation to prove their claim. This often takes the form of an interview by personnel in an immigration department. Depending on the country, this interview is conducted either in the asylum seeker's native language through an interpreter or in an international lingua franca like English. Australia uses the former method, while Germany employs the latter; the Netherlands uses either method depending on the languages involved. Tape recordings of the interview then undergo language analysis, which can be done either by private contractors or within a department of the government. In this analysis, linguistic features of the asylum seeker are used by analysts to make a determination about the speaker's nationality. The reported findings of the linguistic analysis can play a critical role in the government's decision on the refugee status of the asylum seeker.

Language documentation

Language documentation combines anthropological inquiry (into the history and culture of language) with linguistic inquiry, in order to describe languages and their grammars. Lexicography involves the documentation of words that form a vocabulary. Such a documentation of a linguistic vocabulary from a particular language is usually compiled in a dictionary. Computational linguistics is concerned with the statistical or rule-based modeling of natural language from a computational perspective. Specific knowledge of language is applied by speakers during the act of translation and interpretation, as well as in language education – the teaching of a second or foreign language. Policy makers work with governments to implement new plans in education and teaching which are based on linguistic research.

Since the inception of the discipline of linguistics, linguists have been concerned with describing and analysing previously undocumented languages. Starting with Franz Boas in the early 1900s, this became the main focus of American linguistics until the rise of formal linguistics in the mid-20th century. This focus on language documentation was partly motivated by a concern to document the rapidly disappearing languages of indigenous peoples. The ethnographic dimension of the Boasian approach to language description played a role in the development of disciplines such as sociolinguistics, anthropological linguistics, and linguistic anthropology, which investigate the relations between language, culture, and society.

The emphasis on linguistic description and documentation has also gained prominence outside North America, with the documentation of rapidly dying indigenous languages becoming a focus in some university programs in linguistics. Language description is a work-intensive endeavour, usually requiring years of field work in the language concerned, so as to equip the linguist to write a sufficiently accurate reference grammar. Further, the task of documentation requires the linguist to collect a substantial corpus in the language in question, consisting of texts and recordings, both sound and video, which can be stored in an accessible format within open repositories, and used for further research.

Translation

The sub-field of translation includes the translation of written and spoken texts across media, from digital to print and spoken. To translate literally means to transmute the meaning from one language into another. Translators are often employed by organizations such as travel agencies and governmental embassies to facilitate communication between two speakers who do not know each other's language. Translators are also employed to work within computational linguistics setups like Google Translate, which is an automated program to translate words and phrases between any two or more given languages. Translation is also conducted by publishing houses, which convert works of writing from one language to another in order to reach varied audiences. Cross-national and cross-cultural survey research studies employ translation to collect comparable data among multilingual populations. Academic translators specialize in or are familiar with various other disciplines such as technology, science, law, economics, etc.

Clinical linguistics

Clinical linguistics is the application of linguistic theory to the field of speech-language pathology. Speech language pathologists work on corrective measures to treat communication and swallowing disorders.

Computational linguistics

Computational linguistics is the study of linguistic issues in a way that is "computationally responsible", i.e., taking careful note of computational consideration of algorithmic specification and computational complexity, so that the linguistic theories devised can be shown to exhibit certain desirable computational properties and their implementations. Computational linguists also work on computer language and software development.

Evolutionary linguistics

Evolutionary linguistics is a sociobiological approach to analyzing the emergence of the language faculty through human evolution, and also the application of evolutionary theory to the study of cultural evolution among different languages. It is also a study of the dispersal of various languages across the globe, through movements among ancient communities.

Forensic linguistics

Forensic linguistics is the application of linguistic analysis to forensics. Forensic analysis investigates the style, language, lexical use, and other linguistic and grammatical features used in the legal context to provide evidence in courts of law. Forensic linguists have also used their expertise in the framework of criminal cases.

History of cancer

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/History_of_cancer
A tumor removed by surgery in 1689.

The history of cancer describes the development of the field of oncology and its role in the history of medicine. It also covers its role in the history of public health, of hospitals, and social and cultural history.

Early diagnosis

In 2016, a 1.7 million year old osteosarcoma was reported by Dr Edward John Odes (a doctoral student in Anatomical Sciences from the University of the Witwatersrand Medical School, South Africa) and colleagues, representing the oldest documented malignant hominin cancer.

The earliest known descriptions of cancer appear in several papyri from ancient Egypt. The Edwin Smith Papyrus was written around 1600 BC (possibly a fragmentary copy of a text from 2500 BC) and contains a description of cancer, as well as a procedure to remove breast tumours by cauterization, stating that the disease has no treatment. However, incidents of cancer were rare. In a study by the University of Manchester, only one case was found "in the investigation of hundreds of Egyptian mummies, with few references to cancer in literary evidence."

Hippocrates (c. 460 BCc. 370 BC) described several kinds of cancer, referring to them by the term καρκινος (carcinos), the Greek word for 'crab' or 'crayfish', as well as carcinoma. This comes from the appearance of the cut surface of a solid malignant tumour, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name". Since it was against Greek tradition to open the body, Hippocrates only described and made drawings of outwardly visible tumours on the skin, nose, and breasts. Treatment was based on the humour theory of four bodily fluids (black and yellow bile, blood, and phlegm). According to the patient's humour, treatment consisted of diet, blood-letting, and/or laxatives. Celsus (c. 25 BC – 50 AD) translated carcinos into cancer, the Latin word for crab or crayfish.

In the 2nd century AD, the Greek physician Galen used oncos (Greek for 'swelling') to describe all tumours, reserving Hippocrates' term carcinos for malignant tumours. Galen also used the suffix -oma to indicate cancerous lesions. It is from Galen's usage that we derive the modern word oncology.

Through the centuries it was discovered that cancer could occur anywhere in the body, but Hippocrates' humour-theory-based treatment remained popular until the 19th century.

16th–19th century

A surgical operation to remove a malignant tumor, 1817

In the 16th and 17th centuries, it became more acceptable for doctors to dissect bodies to discover the cause of death. The German professor Wilhelm Fabry believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor Francois de la Boe Sylvius, a follower of Descartes, believed that all disease was the outcome of chemical processes, and that acidic lymph fluid was the cause of cancer. His contemporary Nicolaes Tulp believed that cancer was a poison that slowly spreads, and concluded that it was contagious. In the 1600s, cancer was vulgarly called "the wolf[e]".

The first cause of cancer was identified by British surgeon Percivall Pott, who discovered in 1775 that cancer of the scrotum was a common disease among chimney sweeps. The work of other individual physicians led to various insights, but when physicians started working together they could draw firmer conclusions.

With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' eventually spreads from the primary tumour through the lymph nodes to other sites ("metastasis"). This view of the disease was first formulated by the English surgeon Campbell De Morgan between 1871 and 1874. The use of surgery to treat cancer had poor results due to problems with hygiene. The renowned Scottish surgeon Alexander Monro saw only 2 breast tumour patients out of 60 surviving surgery for two years. In the 19th century, asepsis improved surgical hygiene and as the survival statistics went up, surgical removal of the tumour became the primary treatment for cancer. With the exception of William Coley who in the late 19th century felt that the rate of cure after surgery had been higher before asepsis (and who injected bacteria into tumours with mixed results), cancer treatment became dependent on the individual art of the surgeon at removing a tumour. The underlying cause of his results might be that infection stimulates the immune system to destroy left tumour cells. During the same period, the idea that the body was made up of various tissues, that in turn were made up of millions of cells, laid rest the ancient belief in humor theory on chemical imbalances in the body.

Mechanism

1938 American Society for the Control of Cancer poster.

The genetic basis of cancer was recognised in 1902 by the German zoologist Theodor Boveri, professor of zoology at Munich and later in Würzburg. He discovered a method to generate cells with multiple copies of the centrosome, a structure he discovered and named. He postulated that chromosomes were distinct and transmitted different inheritance factors. He suggested that mutations of the chromosomes could generate a cell with unlimited growth potential which could be passed on to its descendants. He proposed the existence of cell cycle checkpoints, tumour suppressor genes and oncogenes. He speculated that cancers might be caused or promoted by radiation, physical or chemical injuries, or by pathogenic microorganisms.

1938 poster identifying surgery, x-rays and radium as the proper treatments for cancer.

Therapies

When Marie Curie and Pierre Curie discovered radiation at the end of the 19th century, they stumbled upon the first effective non-surgical cancer treatment. With radiation also came the first signs of multi-disciplinary approaches to cancer treatment. The surgeon was no longer operating in isolation but worked together with hospital radiologists to help patients. The complications in communication this brought, along with the necessity of the patient's treatment in a hospital facility rather than at home, also created a parallel process of compiling patient data into hospital files, which in turn led to the first statistical patient studies.

The American Cancer Society was founded in 1913 by 15 physicians and businessmen in New York City under the name American Society for the Control of Cancer (ASCC). The current name was adopted in 1945.

A founding paper of cancer epidemiology was the work of Janet Lane-Claypon, who published a comparative study in 1926 of 500 breast cancer cases and 500 control patients of the same background and lifestyle for the British Ministry of Health. Her groundbreaking work on cancer epidemiology was carried on by Richard Doll and Austin Bradford Hill, who published "Lung Cancer and Other Causes of Death In Relation to Smoking. A Second Report on the Mortality of British Doctors" followed in 1956 (otherwise known as the British doctors study). Richard Doll left the London Medical Research Centre (MRC), to start the Oxford unit for Cancer epidemiology in 1968. With the use of computers, the unit was the first to compile large amounts of cancer data. Modern epidemiological methods are closely linked to current concepts of disease and public health policy. Over the past 50 years, great efforts have been spent on gathering data across medical practice, hospital, provincial, state, and even country boundaries to study the interdependence of environmental and cultural factors on cancer incidence.

Cancer patient treatment and studies were restricted to individual physicians' practices until World War II when medical research centres discovered that there were large international differences in disease incidence. This insight drove national public health bodies to enable the compilation of health data across practices and hospitals, a process found in many countries today. The Japanese medical community observed that the bone marrow of victims of the atomic bombings of Hiroshima and Nagasaki was completely destroyed. They concluded that diseased bone marrow could also be destroyed with radiation, and this led to the development of bone marrow transplants for leukemia. Since World War II, trends in cancer treatment are to improve on a micro-level the existing treatment methods, standardize them, and globalize them to find cures through epidemiology and international partnerships.

In 1968 Michael A. Epstein, Bert Achong, and Yvonne Barr identified the first human cancer virus, called the Epstein–Barr virus.

War on Cancer

The 'war' on cancer in the U.S. focused on the expansion of research on causes and cures. It began with the National Cancer Act of 1971 The act was intended "to amend the Public Health Service Act so as to strengthen the National Cancer Institute in order to more effectively carry out the national effort against cancer". It was signed into law by then President Richard Nixon on December 23, 1971.

In 1973, cancer research led to a Cold War incident, where co-operative samples of reported oncoviruses were discovered to be contaminated by HeLa.

In 1984, Harald zur Hausen discovered first HPV16 and then HPV18 responsible for approximately 70% of cervical cancers. For discovery that human papillomaviruses (HPV) cause human cancer, zur Hausen won a 2008 Nobel Prize.

From 1971 to 2007 the United States invested over $200 billion on cancer research; that total includes funding from public and private sectors and foundations.

Despite this substantial investment, the country saw just a five percent decrease in the cancer death rate (adjusting for size and age of the population) between 1950 and 2005. Longer life expectancy may be a contributing factor to this, as cancer rates and mortality rates increase significantly with age. More than three out of five cancers are diagnosed in people aged 65 and over.

Thursday, April 10, 2025

Gastroenteritis

From Wikipedia, the free encyclopedia
Gastroenteritis
Other namesGastro, stomach bug, stomach virus, stomach flu, gastric flu, gastrointestinitis, flu bug
Gastroenteritis viruses: A = rotavirus, B = adenovirus, C = norovirus and D = astrovirus. The virus particles are shown at the same magnification to allow size comparison.

 
SpecialtyInfectious disease, gastroenterology
SymptomsDiarrhea, vomiting, abdominal pain, fever
ComplicationsDehydration
CausesViruses, bacteria, parasites, fungi
Diagnostic methodBased on symptoms, occasionally stool culture
Differential diagnosisInflammatory bowel disease, malabsorption syndrome, lactose intolerance
PreventionHand washing, drinking clean water, proper disposal of human waste, breastfeeding
TreatmentOral rehydration solution (combination of water, salts, and sugar), intravenous fluids
Frequency2.4 billion (2015)
Deaths1.3 million (2015)

Gastroenteritis, also known as infectious diarrhea, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration may also occur. This typically lasts less than two weeks. Although it is not related to influenza, in the U.S it is sometimes called the "stomach flu".

Gastroenteritis is usually caused by viruses; however, gut bacteria, parasites, and fungi can also cause gastroenteritis. In children, rotavirus is the most common cause of severe disease. In adults, norovirus and Campylobacter are common causes. Eating improperly prepared food, drinking contaminated water or close contact with a person who is infected can spread the disease. Treatment is generally the same with or without a definitive diagnosis, so testing to confirm is usually not needed.

For young children in impoverished countries, prevention includes hand washing with soap, drinking clean water, breastfeeding babies instead of using formula, and proper disposal of human waste. The rotavirus vaccine is recommended as a prevention for children. Treatment involves getting enough fluids. For mild or moderate cases, this can typically be achieved by drinking oral rehydration solution (a combination of water, salts and sugar). In those who are breastfed, continued breastfeeding is recommended. For more severe cases, intravenous fluids may be needed. Fluids may also be given by a nasogastric tube. Zinc supplementation is recommended in children. Antibiotics are generally not needed. However, antibiotics are recommended for young children with a fever and bloody diarrhea.

In 2015, there were two billion cases of gastroenteritis, resulting in 1.3 million deaths globally. Children and those in the developing world are affected the most. In 2011, there were about 1.7 billion cases, resulting in about 700,000 deaths of children under the age of five. In the developing world, children less than two years of age frequently get six or more infections a year. It is less common in adults, partly due to the development of immunity.

Signs and symptoms

Bristol stool chart

Gastroenteritis usually involves both diarrhea and vomiting. Sometimes, only one or the other is present. This may be accompanied by abdominal cramps. Signs and symptoms usually begin 12–72 hours after contracting the infectious agent. If due to a virus, the condition usually resolves within one week. Some viral infections also involve fever, fatigue, headache and muscle pain. If the stool is bloody, the cause is less likely to be viral and more likely to be bacterial. Some bacterial infections cause severe abdominal pain and may persist for several weeks.

Children infected with rotavirus usually make a full recovery within three to eight days. However, in poor countries treatment for severe infections is often out of reach and persistent diarrhea is common. Dehydration is a common complication of diarrhea. Severe dehydration in children may be recognized if the skin color and position returns slowly when pressed. This is called "prolonged capillary refill" and "poor skin turgor". Abnormal breathing is another sign of severe dehydration. Repeat infections are typically seen in areas with poor sanitation, and malnutrition. Stunted growth and long-term cognitive delays can result.

Reactive arthritis occurs in 1% of people following infections with Campylobacter species. Guillain–Barré syndrome occurs in 0.1%. Hemolytic uremic syndrome (HUS) may occur due to infection with Shiga toxin-producing Escherichia coli or Shigella species. HUS causes low platelet counts, poor kidney function, and low red blood cell count (due to their breakdown). Children are more predisposed to getting HUS than adults. Some viral infections may produce benign infantile seizures.

Cause

Viruses (particularly rotavirus (in children) and norovirus (in adults)) and the bacteria Escherichia coli and Campylobacter species are the primary causes of gastroenteritis. There are, however, many other infectious agents that can cause this syndrome including parasites and fungi. Non-infectious causes are seen on occasion, but they are less likely than a viral or bacterial cause. Risk of infection is higher in children due to their lack of immunity. Children are also at higher risk because they are less likely to practice good hygiene habits. Children living in areas without easy access to water and soap are especially vulnerable.

Viral

Rotaviruses, noroviruses, adenoviruses, and astroviruses are known to cause viral gastroenteritis. Rotavirus is the most common cause of gastroenteritis in children, and produces similar rates in both the developed and developing world. Viruses cause about 70% of episodes of infectious diarrhea in the pediatric age group. Rotavirus is a less common cause in adults due to acquired immunity. Norovirus is the cause in about 18% of all cases. Generally speaking, viral gastroenteritis accounts for 21–40% of the cases of infectious diarrhea in developed countries.

Norovirus is the leading cause of gastroenteritis among adults in America accounting for about 90% of viral gastroenteritis outbreaks. These localized epidemics typically occur when groups of people spend time proximate to each other, such as on cruise ships, in hospitals, or in restaurants. People may remain infectious even after their diarrhea has ended. Norovirus is the cause of about 10% of cases in children.

Bacterial

Salmonella enterica serovar Typhimurium (ATCC 14028) as seen with a microscope at 1000 fold magnification and following Gram staining

In some countries, Campylobacter jejuni is the primary cause of bacterial gastroenteritis, with half of these cases associated with exposure to poultry. In children, bacteria are the cause in about 15% of cases, with the most common types being Escherichia coli, Salmonella, Shigella, and Campylobacter species. If food becomes contaminated with bacteria and remains at room temperature for several hours, the bacteria multiply and increase the risk of infection in those who consume the food. Some foods commonly associated with illness include raw or undercooked meat, poultry, seafood, and eggs; raw sprouts; unpasteurized milk and soft cheeses; and fruit and vegetable juices. In the developing world, especially sub-Saharan Africa and Asia, cholera is a common cause of gastroenteritis. This infection is usually transmitted by contaminated water or food.

Toxigenic Clostridioides difficile is an important cause of diarrhea that occurs more often in the elderly. Infants can carry these bacteria without developing symptoms. It is a common cause of diarrhea in those who are hospitalized and is frequently associated with antibiotic use. Staphylococcus aureus infectious diarrhea may also occur in those who have used antibiotics. Acute "traveler's diarrhea" is usually a type of bacterial gastroenteritis, while the persistent form is usually parasitic. Acid-suppressing medication appears to increase the risk of significant infection after exposure to several organisms, including Clostridioides difficile, Salmonella, and Campylobacter species. The risk is greater in those taking proton pump inhibitors than with H2 antagonists.

Parasitic

A number of parasites can cause gastroenteritis. Giardia lamblia is most common, but Entamoeba histolytica, Cryptosporidium spp., and other species have also been implicated. As a group, these agents comprise about 10% of cases in children. Giardia occurs more commonly in the developing world, but this type of illness can occur nearly everywhere. It occurs more commonly in persons who have traveled to areas with high prevalence, children who attend day care, men who have sex with men, and following disasters.

Transmission

Transmission may occur from drinking contaminated water or when people share personal objects. Water quality typically worsens during the rainy season and outbreaks are more common at this time. In areas with four seasons, infections are more common in the winter. Worldwide, bottle-feeding of babies with improperly sanitized bottles is a significant cause. Transmission rates are also related to poor hygiene, (especially among children), in crowded households, and in those with poor nutritional status. Adults who have developed immunities might still carry certain organisms without exhibiting symptoms. Thus, adults can become natural reservoirs of certain diseases. While some agents (such as Shigella) only occur in primates, others (such as Giardia) may occur in a wide variety of animals.

Non-infectious

There are a number of non-infectious causes of inflammation of the gastrointestinal tract. Some of the more common include medications (like NSAIDs), certain foods such as lactose (in those who are intolerant), and gluten (in those with celiac disease). Crohn's disease is also a non-infectious cause of (often severe) gastroenteritis. Disease secondary to toxins may also occur. Some food-related conditions associated with nausea, vomiting, and diarrhea include: ciguatera poisoning due to consumption of contaminated predatory fish, scombroid associated with the consumption of certain types of spoiled fish, tetrodotoxin poisoning from the consumption of puffer fish among others, and botulism typically due to improperly preserved food.

In the United States, rates of emergency department use for noninfectious gastroenteritis dropped 30% from 2006 until 2011. Of the twenty most common conditions seen in the emergency department, rates of noninfectious gastroenteritis had the largest decrease in visits in that time period.

Pathophysiology

Gastroenteritis is defined as vomiting or diarrhea due to inflammation of the small or large bowel, often due to infection. The changes in the small bowel are typically noninflammatory, while the ones in the large bowel are inflammatory. The number of pathogens required to cause an infection varies from as few as one (for Cryptosporidium) to as many as 108 (for Vibrio cholerae).

Diagnosis

Gastroenteritis is typically diagnosed clinically, based on a person's signs and symptoms. Determining the exact cause is usually not needed as it does not alter the management of the condition.

However, stool cultures should be performed in those with blood in the stool, those who might have been exposed to food poisoning, and those who have recently traveled to the developing world. It may also be appropriate in children younger than 5, old people, and those with poor immune function. Diagnostic testing may also be done for surveillance. As hypoglycemia occurs in approximately 10% of infants and young children, measuring serum glucose in this population is recommended. Electrolytes and kidney function should also be checked when there is a concern about severe dehydration.

Dehydration

A determination of whether or not the person has dehydration is an important part of the assessment, with dehydration typically divided into mild (3–5%), moderate (6–9%), and severe (≥10%) cases. In children, the most accurate signs of moderate or severe dehydration are a prolonged capillary refill, poor skin turgor, and abnormal breathing. Other useful findings (when used in combination) include sunken eyes, decreased activity, a lack of tears, and a dry mouth. A normal urinary output and oral fluid intake is reassuring. Laboratory testing is of little clinical benefit in determining the degree of dehydration. Thus the use of urine testing or ultrasounds is generally not needed.

Differential diagnosis

Other potential causes of signs and symptoms that mimic those seen in gastroenteritis that need to be ruled out include appendicitis, volvulus, inflammatory bowel disease, urinary tract infections, and diabetes mellitus. Pancreatic insufficiency, short bowel syndrome, Whipple's disease, coeliac disease, and laxative abuse should also be considered. The differential diagnosis can be complicated somewhat if the person exhibits only vomiting or diarrhea (rather than both).

Appendicitis may present with vomiting, abdominal pain, and a small amount of diarrhea in up to 33% of cases. This is in contrast to the large amount of diarrhea that is typical of gastroenteritis. Infections of the lungs or urinary tract in children may also cause vomiting or diarrhea. Classical diabetic ketoacidosis (DKA) presents with abdominal pain, nausea, and vomiting, but without diarrhea. One study found that 17% of children with DKA were initially diagnosed as having gastroenteritis.

Prevention

Percentage of rotavirus tests with positive results, by surveillance week, United States, July 2000 – June 2009

Water, sanitation, hygiene

A supply of easily accessible uncontaminated water and good sanitation practices are important for reducing rates of infection and clinically significant gastroenteritis. Personal hygiene measures (such as hand washing with soap) have been found to decrease rates of gastroenteritis in both the developing and developed world by as much as 30%. Alcohol-based gels may also be effective. Food or drink that is thought to be contaminated should be avoided. Breastfeeding is important, especially in places with poor hygiene, as is improvement of hygiene generally. Breast milk reduces both the frequency of infections and their duration.

Vaccination

Due to both its effectiveness and safety, in 2009 the World Health Organization recommended that the rotavirus vaccine be offered to all children globally. Two commercial rotavirus vaccines exist and several more are in development. In Africa and Asia these vaccines reduced severe disease among infants and countries that have put in place national immunization programs have seen a decline in the rates and severity of disease. This vaccine may also prevent illness in non-vaccinated children by reducing the number of circulating infections. Since 2000, the implementation of a rotavirus vaccination program in the United States has substantially decreased the number of cases of diarrhea by as much as 80 percent. The first dose of vaccine should be given to infants between 6 and 15 weeks of age. The oral cholera vaccine has been found to be 50–60% effective over two years.

There are a number of vaccines against gastroenteritis in development. For example, vaccines against Shigella and enterotoxigenic Escherichia coli (ETEC), which are two of the leading bacterial causes of gastroenteritis worldwide.

Management

Gastroenteritis is usually an acute and self-limiting disease that does not require medication. The preferred treatment in those with mild to moderate dehydration is oral rehydration therapy (ORT). For children at risk of dehydration from vomiting, taking a single dose of the anti vomiting medication metoclopramide or ondansetron, may be helpful, and butylscopolamine is useful in treating abdominal pain.

Rehydration

The primary treatment of gastroenteritis in both children and adults is rehydration. This is preferably achieved by drinking rehydration solution, although intravenous delivery may be required if there is a decreased level of consciousness or if dehydration is severe. Drinking replacement therapy products made with complex carbohydrates (i.e. those made from wheat or rice) may be superior to those based on simple sugars. Drinks especially high in simple sugars, such as soft drinks and fruit juices, are not recommended in children under five years of age as they may increase diarrhea. Plain water may be used if more specific ORT preparations are unavailable or the person is not willing to drink them. A nasogastric tube can be used in young children to administer fluids if warranted. In those who require intravenous fluids, one to four hours' worth is often sufficient.

Dietary

It is recommended that breast-fed infants continue to be nursed in the usual fashion, and that formula-fed infants continue their formula immediately after rehydration with ORT. Lactose-free or lactose-reduced formulas usually are not necessary. Children should continue their usual diet during episodes of diarrhea with the exception that foods high in simple sugars should be avoided. The BRAT diet (bananas, rice, applesauce, toast and tea) is no longer recommended, as it contains insufficient nutrients and has no benefit over normal feeding.

A Cochrane Review from 2020 concludes that probiotics make little or no difference to people who have diarrhea lasting 2 days or longer and that there is no proof that they reduce its duration. They may be useful in preventing and treating antibiotic associated diarrhea. Fermented milk products (such as yogurt) are similarly beneficial. Zinc supplementation appears to be effective in both treating and preventing diarrhea among children in the developing world.

Antiemetics

Antiemetic medications may be helpful for treating vomiting in children. Ondansetron has some utility, with a single dose being associated with less need for intravenous fluids, fewer hospitalizations, and decreased vomiting. Metoclopramide might also be helpful. However, the use of ondansetron might possibly be linked to an increased rate of return to hospital in children. The intravenous preparation of ondansetron may be given orally if clinical judgment warrants. Dimenhydrinate, while reducing vomiting, does not appear to have a significant clinical benefit.

Antibiotics

Antibiotics are not usually used for gastroenteritis, although they are sometimes recommended if symptoms are particularly severe or if a susceptible bacterial cause is isolated or suspected. If antibiotics are to be employed, a macrolide (such as azithromycin) is preferred over a fluoroquinolone due to higher rates of resistance to the latter. Pseudomembranous colitis, usually caused by antibiotic use, is managed by discontinuing the causative agent and treating it with either metronidazole or vancomycin. Bacteria and protozoans that are amenable to treatment include Shigella Salmonella typhi, and Giardia species. In those with Giardia species or Entamoeba histolytica, tinidazole treatment is recommended and superior to metronidazole. The World Health Organization (WHO) recommends the use of antibiotics in young children who have both bloody diarrhea and fever.

Antimotility agents

Antimotility medication has a theoretical risk of causing complications, and although clinical experience has shown this to be unlikely, these drugs are discouraged in people with bloody diarrhea or diarrhea that is complicated by fever. Loperamide, an opioid analogue, is commonly used for the symptomatic treatment of diarrhea. Loperamide is not recommended in children, however, as it may cross the immature blood–brain barrier and cause toxicity. Bismuth subsalicylate, an insoluble complex of trivalent bismuth and salicylate, can be used in mild to moderate cases, but salicylate toxicity is theoretically possible.

Epidemiology

Deaths due to diarrhoeal diseases per million persons in 2012
  0–2
  3–10
  11–18
  19–30
  31–46
  47–80
  81–221
  222–450
  451–606
  607–1799
Disability-adjusted life year for diarrhea per 100,000 inhabitants in 2004

It is estimated that there were two billion cases of gastroenteritis that resulted in 1.3 million deaths globally in 2015. Children and those in the developing world are most commonly affected. As of 2011, in those younger than five, there were about 1.7 billion cases resulting in 0.7 million deaths, with most of these occurring in the world's poorest nations. More than 450,000 of these fatalities are due to rotavirus in children under five years of age. Cholera causes about three to five million cases of disease and kills approximately 100,000 people yearly. In the developing world, children less than two years of age frequently get six or more infections a year that result in significant gastroenteritis. It is less common in adults, partly due to the development of acquired immunity.

In 1980, gastroenteritis from all causes caused 4.6 million deaths in children, with the majority occurring in the developing world. Death rates were reduced significantly (to approximately 1.5 million deaths annually) by 2000, largely due to the introduction and widespread use of oral rehydration therapy. In the US, infections causing gastroenteritis are the second most common infection (after the common cold), and they result in between 200 and 375 million cases of acute diarrhea and approximately ten thousand deaths annually, with 150 to 300 of these deaths in children less than five years of age.

Society and culture

Gastroenteritis is associated with many colloquial names, including "Montezuma's revenge", "Delhi belly", "la turista", and "back door sprint", among others. It has played a role in many military campaigns and is believed to be the origin of the term "no guts no glory".

Gastroenteritis is the main reason for 3.7 million visits to physicians a year in the United States and 3 million visits in France. In the United States gastroenteritis as a whole is believed to result in costs of US$23 billion per year, with rotavirus alone resulting in estimated costs of US$1 billion a year.

Terminology

The first usage of "gastroenteritis" was in 1825. Before this time it was commonly known as typhoid fever or "cholera morbus", among others, or less specifically as "griping of the guts", "surfeit", "flux", "colic", "bowel complaint", or any one of several other archaic names for acute diarrhea. Cholera morbus is a historical term that was used to refer to gastroenteritis rather than specifically cholera.

Animals

Many of the same agents cause gastroenteritis in cats and dogs as in humans. The most common organisms are Campylobacter, Clostridioides difficile, Clostridium perfringens, and Salmonella. A large number of toxic plants may also cause symptoms.

Some agents are more specific to a certain species. Transmissible gastroenteritis coronavirus (TGEV) occurs in pigs resulting in vomiting, diarrhea, and dehydration. It is believed to be introduced to pigs by wild birds and there is no specific treatment available. It is not transmissible to humans.

Comparative genomics

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Comparative_genomics   ...