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QUESTION ONESOURCES OF EPIDEMIOLOGICAL DATAThere are different sources of data on health and health related conditions in the community. The World Health Organization listed the following as key sources of surveillance data: Mortality reports Morbidity reports Epidemic reports Reports of laboratory utilization (including laboratory test results) Reports of individual case investigations Reports of epidemic investigations Special surveys (e.g., hospital admissions, disease registers, and serologic surveys) Information on animal reservoirs and vectors Demographic data Environmental dataa) Mortality DataVital statisticsVital statistics include data on birth, death, marriage, and divorce. Records may be available at the local and state level within a matter of days or weeks, but they are not always coded or computerized. Medical examiner dataCoroners and medical examiners can provide information on sudden or unexpected deaths. Their reports are available at the state or county level, and include details about the cause and nature of death that are not given on the death certificate. These reports are particularly valuable for surveillance of intentional and unintentional injuries and of sudden deaths of unknown cause.b) Morbidity DataNotifiable disease reportsEach county government establishes what health events must be reported by health care providers in that county. An outbreak of any condition should be reported. Health agencies at the local, county, and national level routinely use the reported data for public health surveillance.

Laboratory dataLaboratory reports form the basis of surveillance for selected diseases, including many viral illnesses and those caused by enteric pathogens such as Salmonella and Shigella. These may or may not be part of the notifiable disease reporting system.Hospital dataMany hospitals have computerized discharge records, primarily for financial purposes. These records may be used for surveillance purposes. These records typically include demographic data, diagnoses, operative procedures, length of stay, and costs, but exclude names, addresses, and other information which could identify individuals.c) Surveys of Health and General PopulationsHealth surveys are studies conducted on a representative sample population to obtain more comprehensive data for monitoring the health status of a population. d) Surveillance Systems of Disease IndicatorsStill other surveillance systems collect data on indicators of disease or of disease potential. These systems fall into four categories: animal populations, environmental data, drug/biologic utilization, and student and employee data. Of these categories, the animal and environmental systems act as early-warning systems of disease potential. The other two categories collect disease-indicator data that are more accessible than data on the particular diseases themselves.Each of these categories is described in more detail below.Animal populationsMonitoring animal populations is an important part of the surveillance system for certain diseases. Animal surveillance may include detecting and measuring:1. Animal morbidity and mortality caused by a disease that can affect humans (e.g., rabies)2. The presence of a disease agent in wild and domestic sentinel animals (e.g., survey of rodents for plague, of chickens for St. Louis encephalitis)3. Changes in the size and distribution of the animal reservoirs and vectors of a disease (e.g. monitoring deer and ticks which are hosts for the agent that causes Lyme disease)Environmental dataPublic health agencies conduct routine environmental surveillance at the community level to detect contamination of public water, milk, and food supplies. Agencies may also use environmental surveillance to focus on conditions in nature that support animal populations that may be reservoirs or vectors of disease. For example, agencies may monitor tire dumps and other potential breeding sites for mosquitoes. Other types of environmental surveillance have become important in recent years, such as environmental monitoring for radiation. In the workplace hazard surveillance, such as monitoring potentially harmful chemical, biological, and physical agents, guides strategies for preventing illness and injury.Student and employee dataPublic health agencies may use school absenteeism records to assess the pervasiveness of influenza-like illness in a community. Employee records, workers compensation claims, and other occupational data are increasingly being used for surveillance of occupational illness and injuries.e) Census:Census is defined as a periodic count or enumeration of a population. Census data are necessary for accurate description of populations health status and are principal source of denominator for rates of disease & death. From these data different health indices could be calculated. Crude birth rate, crude death rate, age specific mortality rate and sex specific mortality rate are some of the examples of the indicators that could be calculated.QUESTION TWOUses of Epidemiology data

a) To make a community diagnosis. Epidemiology helps to identify and describe health problems in a community (for example, the prevalence of anaemia, or the nutrition status of children).b) To monitor continuously over a period of time the change of health in a community. (for example, the effect of a vaccination programme, health education, nutritional supplementation).c) To practice surveillance for a specific disease in order to be able to act quickly and so cut short any outbreak (example cholera).d) To investigate an outbreak of a communicable disease, analyse the reasons for it, plan a feasible remedy and carry it out, and monitor the effects of the remedy on the outbreak.e) To plan effective health services. Effective services, interventions and remedies all depend on accurate community data.

REFERENCES 1. R. Bonita, R. Beaglehole, T. Kjellstrm. 2006. Basic epidemiology. 2nd edition. WHO.2. Yigzaw Kebede. 2004. Epidemiology lecture notes for Environmental and Occupational Health Students. University of Gondar: Ethiopia Public Health Training Initiative. Ethiopia.3. http://gwxy.sysu.edu.cn/lxbx/english/epidemiologic%20knowledge/Scope%20and%20Significance%20of%20Epidemiology/import.html