Virus outbreaks occur when a virus bypasses infection control measures and a relatively high number of infections are observed where no cases or sporadic cases occurred in the past. The study of pathogenic viral outbreaks is a branch of epidemiology and usually refers to virus outbreaks that make people, animals, or plants sick. As with bacterial outbreaks, viral outbreaks are classified as sporadic (occasional occurrence), endemic (regular cases often occurring in a region), epidemic (an unusually high number of cases in a region), or pandemic (a global epidemic).

Major human epidemic viruses include influenza, Human Immunodeficiancy Virus (HIV), measles, and rubella. Smallpox has been eradicated as a major epidemic virus, however emerging viruses and engineered viruses pose a significant challenge for the future. HIV is no longer considered an emerging virus as it was discovered over 20 years ago, and it has grown to become a major epidemic. Other emerging viruses include Severe Acute Respiratory Syndrome (SARS), henipaviruses and Ebola which have been contained through aggressive contact tracing and isolation of patients and suspected carriers of the disease.

Hoof and mouth disease (UK foot and mouth disease) is a major animal epidemic virus affecting the agricultural industry of any country with an outbreak. It affects cows, pigs, sheep, goats, deer and other cloven hoofed animals.

See also:

epidemiology, bacterium, virus

Outbreak (film) was the name of a film.