Keeping the world safe from disease requires an ongoing effort by governments, communities, families and individuals. Vaccination, regular hand washing, covering sneeze and cough, and isolating ill people are just some of the many steps necessary to prevent the spread of disease. Civil society groups can play a vital role in mediating between government and communities, and raising awareness about disease threats. It is also important for people to take preventive measures when traveling abroad, or living in underdeveloped areas where there are higher disease risks. It is recommended to seek advice from a reliable source before travel, and to always be aware of the latest health threats to avoid diseases like influenza A (H1N1), measles, cholera, malaria, MDR-TB, or bloody diarrhea.

A disease outbreak is defined as a larger-than-expected number of cases of the same illness in a specific place and time. This could be as small as a single school or restaurant, or as large as an entire nation or continent. The number of cases should be compared with the expected numbers using data from public health departments, disease registries or hospital discharge records. Possible biases which may affect the evaluation of cases, such as variations in reporting procedures or screening campaigns, must be taken into account.

Descriptive epidemiology is a fundamental tool of outbreak investigations and allows the establishment of specific hypotheses about the disease. Moreover, it serves as the basis for developing public health regulations and prevention guidelines.