Viruses are obligate intracellular parasites that require living host cells to grow and reproduce. Adenovirus is not new, but with recent attention regarding severe outbreak situations associated with death, the need for review and understanding should be emphasized. Adenovirus, a DNA virus, was first isolated in the 1950s in adenoid tissue–derived cell cultures, hence the name. There are 52 different types of adenovirus. Types 1,2,3 and 5 are most common (type 3 more prevalent during cold weather). Adenovirus is a hardy, non-enveloped virus which means it does not have an outer lipid layer (non-lipid virus) and may be more difficult to kill with low level disinfectants.