poxvirus, (family Poxviridae), any of a group of viruses constituting the family Poxviridae responsible for a wide range of pox diseases in humans and other animals. The family contains various subfamilies and genera.
In terms of human disease, the most important genus is Orthopoxvirus, which contains viruses that cause significant diseases in humans, including smallpox, caused by variola virus; cowpox, caused by vaccinia virus; and mpox, caused by monkeypox virus. Chickenpox, despite its name, is caused by a herpesvirus rather than a poxvirus.
Vaccines have been developed against smallpox, cowpox, and monkeypox viruses; the success of vaccination against variola viruses, beginning with Edward Jenner’s smallpox vaccine, led to the worldwide eradication of smallpox by 1980. The virus of rabbitpox, or infectious myxomatosis, has been used with mixed success in Australia to control wild rabbit populations.
Poxvirus particles are somewhat brick-shaped, the longest dimension being as much as 250–300 nm (nanometres; 1 nm = 10−9 metre). It is surface-studded with hollow spikes and contains deoxyribonucleic acid (DNA). Unlike other DNA viruses, poxviruses appear to develop entirely within the cytoplasm of affected cells.