An epidemic is the occurrence in a community of cases of a disease significantly greater than would be expected under normal circumstances. The word comes from the Greek epidemeo, meaning “to be present in town,” and was used by writers before Hippocrates to describe almost everything except diseases (people, rain, rumors, war). Hippocrates was the first to adapt this term as a medical one.
An outbreak is a group of people exposed to the same disease from the same source, such as a restaurant, hospital or contaminated food supply. A common-source outbreak is further defined by how many people were infected and whether all became ill within a single incubation period (the time it takes for a person to develop symptoms). If fewer than 100 people became ill with the same infectious agent, it’s called a cluster.
Infectious diseases aren’t just bad for our health; they can devastate economies, disrupt societies and even change history. From old plagues like cholera and smallpox to new ones such as severe acute respiratory syndrome and Middle East Respiratory Syndrome, the 21st century has seen more than its share of biological disasters – and we’re only just beginning.
The emergence and spread of infectious diseases is highly unpredictable. To keep up with what’s happening, experts monitor a wide range of sources, including official public health reports, unofficial outbreak aggregators such as ProMED Mail and Outbreak News Today, media reports and trusted social media accounts. We evaluate each outbreak based on its geographic and epidemiological details to identify which ones deserve further investigation. Then we structure these events into comprehensive, structured outbreak datasets that can be used for monitoring, forecasting and risk assessment.