Any previously unknown communicable illness or any previously controlled contagion whose incidence and prevalence are suddenly rising. In recent years, some emerging (and re-emerging) infections have been bovine spongiform encephalopathy (mad cow disease), Ebola hemorrhagic fever, cholera, plague, hemolytic uremic syndrome caused by Escherichia coli 0157:H7, drug-resistant strains of enterococcus, the human immunodeficiency virus, SARS, and antibioticesistant organisms, among many others.
An infectious disease that has witnessed a rise in its occurrence within the past 35 years and is projected to potentially increase further in the immediate future.