Poxviruses

This family includes Molluscum contagiosum virus, vaccinia, and smallpox virus, the first of which is most important for USMLE.

Molluscum Contagiosum Virus

It causes umbilicated lesions on the skin and mucosa in children and immunocompromised individuals in whom the disease is generalized. It is spread by close contact. Clinical diagnosis is made, and infected cells show cytoplasmic inclusions on biopsy.

Smallpox and Vaccinia Virus

Also called Variola. Smallpox has been eradicated from the world. The virus is brick-shaped. The only importance is the potential to be used as a bioterrorism agent. It can spread easily by aerosols. The disease presents as fever and maculopapular rash in a centrifugal distribution.

Vaccinia virus is a nonpathogenic poxvirus that is used for experimental and research purposes.