Surveillance for communicable diseases is the main public health surveillance activity in China. Currently, the disease surveillance system in China has three major components:
- National Disease Reporting System (NDRS): The system covers the entire population (1.3 billion persons) living in all the provinces, prefectures, and counties that make up mainland China. Thirty-five communicable diseases are reportable under this system.
- Nationwide Disease Surveillance Points (DSPs): This surveillance system, comprising 145 reporting sites selected by stratified cluster random sampling, covers a 1% representative sample of China's population.
- Surveillance system for specific infectious diseases, occupational diseases, food poisoning, etc.
Data collected through the disease surveillance network serve as the basis for formulating health policies and devising strategies for preventing disease. A computerized reporting system for notifiable diseases has been established that links China's 30 provinces, autonomous regions, and municipalities. Mechanisms for providing timely feedback to units that report data and for systematically assessing the quality of those data are important attributes of this system.
National Disease Reporting System (NDRS)
In
1959, a system for reporting infectious diseases was established. Data
collected at the village level are reported to prevention units in
township hospitals. From the prevention units, data are transmitted
through county health and epidemic-prevention stations to provincial
centers and then on to the Chinese Academy of Preventive Medicine. Since 1977, the Ministry of Public Health has convened annual meetings to analyze these data on the morbidity and mortality associated with infectious diseases.
In 1987, a Nationwide Antiepidemic Computer Telecommunication Network
(NATCN) was established as an official information system for the
National Disease Reporting System (NDRS). The Ministry of Public Health
and the provincial centers of health and epidemic prevention support
this network, which monitors disease epidemics
at various levels within the public health system. As technical
facilities of the network improve, use of the NACTN will expand into all
aspects of public health surveillance.
Computer Network Development
After
receiving approval from the Ministry of Public Health in 1986, the
Chinese Academy of Preventive Medicine (CAPM) began to establish a
nationwide microcomputer communication network.
The purpose was to link all the country's provincial centers of health
and epidemic prevention in an effort to improve the system for
preventing epidemics. After a year was spent establishing and modifying
the system, a network that connected the capitals of 30 provinces,
autonomous regions, and municipalities began operating in 1987. The
primary function of the network was to collect data on the morbidity and
mortality associated with reportable communicable diseases, to obtain
information on outbreaks of other types of disease, and to provide monthly and annual reports to local and national health authorities.
Morbidity and Mortality Monthly Reports (MMMR)
Each month, all provinces transmit county-level
summaries of the numbers of cases and deaths associated with 35
notifiable communicable diseases to the Academy of Preventive Medicine.
Reports are sent on the 13th to 15th day of each month via the NACTN. At
the central node of NACTN, the Academy's Center of Computer Science and Health Statistics
compiles and analyzes the data, provides feedback to the provinces, and
creates national summaries within one week. Copies of the MMMR are
distributed regularly to health authorities at various levels.
Morbidity and Mortality Annual Report (MMAR)
Each January, all provinces provide supplementary reports to revise and update the monthly reports submitted during the previous year. Age- and occupation-specific
reports of mortality and morbidity are also submitted at this time. In
April, after the surveillance data have been reviewed at the national
meeting on epidemic diseases, the MMAR and other analytical reports are
distributed.
Computer Telecommunication of Surveillance Data: Technical Issues
Until the 1980s, no public digital communications system was available in China. In establishing the nationwide communication network, modems with common analog telephone
lines had to be used. Making this large communication system run
successfully posed major challenges. With some of the problems in mind,
the system was designed to have strong fault-tolerant redundancy - with
the capability for self-correction - to overcome the myriad of problems
caused by poor-quality telephone lines and cumbersome telephone exchange systems.
The NACTN was enhanced by incorporating the following functions.
- Breakpoint recording with resumption of operations: When telephone lines break during data transmission, the system is designed to record the break-point status for every case. This allows data transmission to resume automatically when line connections are reestablished.
- Automatic node scanning and re-circling: This feature allows the system to scan the status of all network nodes to allocate telephone lines and thereby optimize the strategy for maintaining line connections. This important mechanism improves the efficiency of the system and makes data transmission more successful.
- Automatic sorting/batching, rescheduling, and executing of transmissions: The system can execute all necessary network commands to carry out the communication task arranged by command files of the MMMR/MMAR system. The system adjusts the path as needed in order to complete transmissions that have been delayed because of problems in the system.
- Data compression and security: Before transmission, data are processed by a "two-phase compressing" procedure. Data file size can be compressed more than 90%, resulting in shorter online transmission times. Thus, receiving data from the 30 provincial reporting centers on the network requires only about an hour of online operation. Compression also makes data transmission more secure.
System Support for NACTN
- Personnel: In each province, the computer divisions have selected one or two persons who are dedicated to operating the province's nodes of the NACTN. In 1987, a working group convened to coordinate computer applications and activities. Several times each year, persons from provincial centers meet to discuss network problems and to devise solutions.
- Hardware and software: Special software has been developed: YQS for collecting and processing information and producing reports and TXS for managing network communications.
Future Developments of the NACTN
- Accumulating information
- Updating techniques
- Establishing subnetworks within provinces
In collaboration with the NACTN, a few provinces have established subnetworks to facilitate local communication.
Existing Databases
- National report on infectious disease
- National disease surveillance
- National report on occupational disease
- National report on outbreaks of food poisoning
- National survey data bases: Drinking water quality; Human-parasite infections; Nutritional surveys; Nutrition for the elderly; Child-nutrition surveillance; Diarrheal disease of children; Smoking and health.
National Disease Surveillance Points (DSPs)
In
the period 1980–1989, the network of DSPs covered 29 provinces,
autonomous regions, and municipalities that had a combined population of
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Because participation in the network was voluntary, the data collected
were biased, even after attempts were made to adjust the sample to
improve national representativeness. Persons covered by the DSPs tended
to be from the upper-middle socioeconomic stratum.
In 1989, efforts were begun to select a new sample of
surveillance points. We used stratified cluster random sampling to
select 145 DSPs in 30 provinces, autonomous regions, and municipalities,
which have a combined population structure similar to that shown in the
national census. Data on individual births and deaths, as well as on
infectious diseases and certain types of behaviors (e.g., tobacco smoking),
are recorded. At the household level, information on socioeconomic
indicators, health-care conditions, and environmental factors is
collected.
Information obtained from the DSPs is compared with data obtained from the National Disease Reporting System to enable policymakers
to estimate more accurately the burden of morbidity and mortality
associated with infectious disease. More importantly, policy makers can
evaluate information from the DSPs in relation to the economic
development, cultural background, and health-care-service use by the
population covered by this surveillance system.
Data collected at DSPs:
- Household information: includes data on number of members, income, health-care situation, water supply, and toilet facilities.
- Individual information: includes data on occupation, education, births, deaths, episodes of infectious diseases, pregnancy, lactation, feeding, and vaccination status.
Each month, data collected by the township hospitals and village
prevention units are submitted to the country, which then conveys the
information through the provincial centers to the Chinese Academy of
Preventive Medicine. The Academy distributes monthly reports to the
Ministry of Public Health, to provincial health authorities, and to all
DSPs. An annual report is also published and distributed.
Surveys and Investigations
Surveys
and investigations are conducted by the DSPs to improve the quality and
promote the use of data collected. These surveys and investigations are
designed to generate information that can be used by policymakers. At
present, the following activities are being undertaken:
- Characterizing risk factors and patterns of death among adults;
- Identifying factors that influence the quality of data collected by DSPs;
- Developing methods to monitor Chronic diseases in China;
- Devising approaches to promote use of data from DSPs by policymakers.
Development of the Network of Disease Surveillance Points
Samples of persons already monitored under existing DSPs will be used for data collection
to address important and emerging public health issues. Issues to be
addressed include a prospective study of the health consequences of
smoking, an assessment of drinking-water quality and disease occurrence,
an evaluation of the national "Expanded Program on Immunization", and an epidemiologic study of hepatitis.
By selecting samples in this fashion, investigators can correlate data
from these special studies with data routinely collected under the
system of DSPs.
Surveillance of Specific Infectious diseases
The following are examples of surveillance for specific infectious diseases.
- For each 10-day period during the summer, cases of cholera - diagnosed by microbiologic or clinical criteria - from all the provinces, autonomous regions, and municipalities are reported to the national level; this information is compiled and conveyed back to the provincial reporting sources.
- In eight provinces, surveillance among subgroups of the population with elevated risk for infection with human immunodeficiency virus (HIV) is conducted at the national diagnostic laboratories by using immediate reports and confirmatory testing.
- A surveillance network for epidemic hemorrhagic fever has been established for immediate reporting of cases. During the peak season, surveillance for disease among rodents is conducted to provide an early-warning system at the local level.
Quality control of data collection
Quality control (QC) in association with data collection (DC) has been an important component of disease-surveillance activities in China.
- In November of each year, the NDRS actively surveys hospitals and households to identify the proportion of notifiable diseases that went unreported. During a recent year, for example, the proportion of class A and B infectious diseases that was unreported was 27%; this proportion was used to correct the total annual estimate of morbidity attributable to infectious diseases.
- Disease Surveillance Points (DSPs) are surveyed annually to estimate underreporting of births, deaths, and morbidity due to infectious diseases. From 1990 to 1991, for example, reporting of morbidity from infectious diseases improved. The proportions of unreported births, age-specific deaths, and disease-specific deaths are also reported. In 1991, a team from the Chinese Academy of Preventive Medicine evaluated the quality of data reported from 18 DSPs located in nine provinces. In their study, the evaluation team identified factors that influenced data quality.
Use of surveillance data for control of disease
Surveillance data have been used to implement and evaluate public health programs.
- Monitoring morbidity from infectious disease during heavy flooding in 1991
When six provinces around the Yangtze River
were heavily flooded in 1991, the central government expressed serious
concern about disease-prevention activities in these provinces. In
response, experts were dispatched to the flooded area, and prevention
guidelines were developed and distributed to the affected provinces.
Simultaneously, a system for collecting daily reports of disease
activity was established. Every 3 days, DSP data on infectious disease
morbidity were compared with data from previous years to identify
potential outbreaks. For example, rates of hepatitis during the flood
were compared with rates for the comparable time periods from the
preceding 2 years. Data collected from June to October 1991 indicated
that infectious diseases had been controlled effectively during the
flood.
- Forecasting the epidemiologic transition in China
In a study sponsored by the World Bank,
data collected in DSPs in the period 1986-1989 have been used to study
the epidemiologic transition in China. Mortality from leading causes of
death was projected for 2010 and 2030. After risk factors were assessed
and the impact of preventive programs on these chronic diseases
was estimated, mortality rates were recalculated. These analyses were
used to develop recommendations for program planning to the Ministry of
Health.
- Prediction and control of meningitis
After surveillance data on morbidity from meningitis in China were reviewed by empirical analysis and Boyer's Theorem,
it was predicted that morbidity from this disease would peak in 1984 or
1985. Additional analyses suggested that the vaccination program that
had been conducted for several years, which provided vaccination only
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epidemiologic data) identified a high risk of meningitis outbreaks. The results in Henan Province suggested that the intensified vaccination coverage was successful in decreasing rates of meningitis.
- Strategy for vaccination for poliomyelitis
After data from 1988 to 1989 on rates of poliomyelitis
and vaccination coverage were reviewed, high-risk areas were
identified. In these areas, persons received supplementary vaccination
in 1989–1990. By 1991, rates of poliomyelitis had begun to fall.
