Surveillance for communicable diseases is the main public health surveillance activity in China. Currently, the disease surveillance system in China has three major components:[1]
There are 35 notifiable infectious diseases, which are divided into Classes A, B, and C. The functions of the surveillance include explaining the natural history of infectious diseases, describing the distribution of case occurrence, triggering disease-control effort, monitoring epidemic of infectious diseases during natural disasters, predicting and controlling epidemics, and providing the base of policy adjustment.
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.
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.
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.
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.
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.
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.
In collaboration with the NACTN, a few provinces have established subnetworks to facilitate local communication.
In the period 1980–1989, the network of DSPs covered 29 provinces, autonomous regions, and municipalities that had a combined population of 10 million persons (<1% of China's population). When the network was proposed in 1978, it was not possible to obtain a population-based random sample. 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:
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 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:
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.
The following are examples of surveillance for specific infectious diseases.
Quality control (QC) in association with data collection (DC) has been an important component of disease-surveillance activities in China.
Surveillance data have been used to implement and evaluate public health programs.
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.
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.
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 for children <12 months of age, would not be adequate to control the predicted upsurge in disease. Therefore, a new vaccination program was adopted that expanded coverage to all children <5 years of age in areas in which surveillance data (including serum 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.
After data from 1988 to 1989 on rates of poliomyelitis and vaccination coverage were reviewed, and high-risk areas were identified. In these areas, persons received supplementary vaccination in 1989–1990. By 1991, rates of poliomyelitis had begun to fall.