What is public health surveillance? One may ask. Public health surveillance is defined as the ongoing and systematic collection, analysis and interpretation of health data essential to planning, implementation, and evaluation of public health practice and programmes closely integrated with timely dissemination of these data to those who need to know.
The idea of collecting data, analyzing them, and considering a reasonable response stems from Hippocrates, a Greek physician who lived between 460 – 370 BC. In his book, ‘On Airs, Waters, and Places’, when writing on disease occurrence, Hippocrates made a distinction between the endemic state as the steady state of the disease, and the epidemic as the abrupt change in the incidence of disease.
Below are Legislations for surveillance the legislation; in 1741, the legislation for surveillance was first introduced in America, when Rhode Island passed an act requiring tavern keepers to report contagious disease among their patrons. Regular reporting of smallpox, yellow fever, and cholera was made an act. France was the first country to make the health of people as the responsibility of the state. After all these data are collected, they do not rest on the tables of those that collect them, instead, they are used as “INFORMATION FOR ACTION”.
Below are some uses of surveillance, to determine incidence of disease, to know the geographical distribution or spread of disease/event, to identify population at risk of that disease/event, to capture the factors and conditions responsible for occurrence and spread of a disease, to predict the occurrence of epidemic and control epidemic, to evaluate the effectiveness of an intervention or programme, to assess the disease burden in the community or health needs of community, to monitor trend of disease over a long – time period.
Surveillance is not just made anyhow, as far as epidemiology is concerned but instead, certain protocol steps are followed. They are as follows; Detection and notification of health event, Investigation, and confirmation (epidemiological, clinical, laboratory), Collection of data, Analysis and interpretation of data, Action to be taken, Feedback and dissemination of results. The cases that have been detected and recorded need to be compiled and transmitted to the next level on a regular basis once a week or daily.
This could be done on a fixed date from each type of unit. All reporting units or centers will provide zero reporting if no cases were detected. The designation of the person responsible for data compilation and transmission at each level has been identified (pharmacist, computer statistical officer, lab technician and medical officer). The health workers, medical officers of PHCs and sentinel private practitioners will provide regular reports on prescribed formats on every Monday.
After the compilation and interpretation, the analysis should be encouraged at each level of the surveillance system. Data are analyzed by count, divide and compare principles and then displayed by time, place and person analysis. The workers should learn to interpret the data they are collecting and thereby they will have a better understanding of the needs of their community. The surveillance data can be easily tabulated in three ways: summary tables, disease charts, and maps, which show the number of cases of the disease for each reporting week and month. Data after analysis becomes useful information for action.
This is then followed by “action”. Surveillance without action is useless. Action for malaria surveillance is full therapeutic treatment, radical treatment, and selective spray programme and to control the breeding of vector as also to educate people. Similarly, action for the outbreak of polio necessitates mass polio vaccination or outbreak response immunization. An outbreak of viral hepatitis needs super chlorination of water supply or boiling of water apart from personal hygiene.
Surveillance encompasses a wide coverage area and for that matter, there exist different types of surveillance to cover these areas. These types include; Community level surveillance, Routine reporting system, Active and passive surveillance, Sentinel surveillance, Surveys, and special studies, Case and outbreak investigation, Verbal autopsy, Laboratory surveillance, and Entomological surveillance.
With the routine surveillance system, Health staff collects information about a number of cases of reportable diseases and deaths that occur in relation to all national health programmes. This system relies on the government established a system of sub centers, PHCs, CHCs, and hospital data. Whosoever comes to these facilities are recorded and reported. Thus called passive routine reporting system. To ensure that reporting units at various levels remain motivated and involved in the surveillance process, there must be regular communication back from higher levels of programme management to lower levels. The feedback should include comments on the performance and quality in recording and reporting of cases and suggestions in solving problems in the collection of data.
Sentinel surveillance has to do with the selection of a small number of health units to report cases of diseases and deaths that are seen or diagnosed at their facility. These sentinel sites also collect and report additional information such as age, immunization status, and other details. Staff at sentinel sites is given special training and supervised to ensure that reporting is complete and accurate.
This is done in the hospitals (infectious diseases, TB, Pediatric hospital), Health centers, Antenatal clinics, STD clinics, Laboratory, Rehabilitation centers which attend a large number of a particular type of cases. Minimum criteria need to be observed in the selection of sentinel Centre. They are as follows; large attendance of patients with a particular disease, Diagnosis is reasonable, accurate and laboratory support is available, good recording and reporting facilities available and Willingness to submit a regular report.
Sample surveys or disease surveys is an active and efficient method of surveillance, which can complement other methods. Two surveys done at an interval of several years apart may be able to demonstrate changes in disease incidence. The first survey for collecting reliable baseline epidemiological information and the subsequent one for the evaluation of the control programme or intervention. E.g. Survey on blindness at different points in time in India provides information on the prevalence of blindness and the effect of interventions on blindness.
National oral health survey and fluoride mapping provide useful information on oral health status and problems. Survey of the risk factor for no communicable diseases is being undertaken at 3- 5 years interval under IDSP.
That is not to say surveillance is run smoothly. There are some difficulties associated with them. They are; Surveys are difficult to conduct, relatively expensive, highly skilled persons with organizational abilities are required. The sample size, questionnaires, and forms must be well designed to avoid bias and misinterpretation of data, some diseases require laboratory back-up for accurate diagnosis, which makes the surveys even more difficult.
Appiah, Daniel Osei Bonsu
Physician Assistant Student,
The University of Cape Coast,
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