Emerging infectious disease: An infectious disease that has newly appeared in a population or that has been known for some time but is rapidly increasing in incidence or geographic range.
Examples of emerging infectious diseases include:
- Ebola virus (first outbreaks in 1976 and the discovery of the virus in 1977),
- HIV/AIDS (virus first isolated in 1983),
- Hepatitis C (first identified in 1989, now known to be the most common cause of post-transfusion hepatitis worldwide),
- Influenza A(H5N1) virus (well known pathogen in birds but first isolated from humans in 1997),
- Legionella pneumophila (first outbreak in 1976 as Legionnaire disease and since associated with similar outbreaks linked to poorly maintained air conditioning systems),
- E. coli O157:H7 (first detected in 1982, often transmitted through contaminated food, has caused outbreaks of hemolytic uremic syndrome), and
- Borrelia burgdorferi (first detected in 1982 and identified as the cause of Lyme disease).
Another example of an emerging infectious disease is the new variant of Creutzfeldt-Jakob disease, which was first described in 1996. The agent is considered to be the same as that causing bovine spongiform encephalitis, a disease which emerged in the 1980s and affected thousands of cattle in the UK and Europe.