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In emergencies, surveillance is often done for specific diseases. Most commonly, diseases of two types are included in surveillance:
- Those which cause substantial morbidity and/or mortality and need to be controlled, such as malaria, viral diarrhoea, pneumonia (also called lower respiratory infection, or LRI), etc.
- Those which can occur in rapidly developing outbreaks which may cause substantial morbidity and/or mortality, such as measles, meningitis, yellow fever, cholera, etc.
A typical surveillance form completed by health care workers in clinics might look like this:
This form is much simpler than the forms for communicable diseases used in developed countries or in stable populations because:
- Health workers generally do not have access to laboratory facilities; their diagnoses are based only on clinical signs and symptoms and,
- Health workers are often very busy and do not have time to collect much data on each patient.
Health workers merely put a tick in the appropriate box to record each patient. As a result, public health authorities who analyze the data can only count the number of cases for each age and sex group. They know nothing about each individual case.