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(Variola major)

General Information

The last naturally acquired case of smallpox in the world occurred in October 1977 in Somalia. The World Health Organization officially certified the world as smallpox-free in 1979. Two secure laboratories, the Centers for Disease Control and Prevention (CDC) in the United States and one in Russia, are the only known holders of the virus.

Smallpox is spread by droplet and aerosol; it may also be spread by direct inoculation from a lesion to an open wound or cut in the skin. Weaponized smallpox has been postulated to be spread by aerosol. Transmission is usually limited to close contacts such as household members. The incubation period is from seven to 17 days; patients are infectious once the rash and/or oral lesion has appeared.

Smallpox disease is distinct from other general body rashes.

CDC: Smallpox Basics

Information for Providers

This is a Wisconsin disease surveillance category I disease:

  • Report IMMEDIATELY by TELEPHONE to the patient's local public health department upon identification of a confirmed or suspected case. The local health department shall then notify the state epidemiologist immediately of any confirmed or suspected cases. Submit a case report within 24 hours electronically through the Wisconsin Electronic Surveillance System (WEDSS), by mail or fax using an Acute and Communicable Disease case report, F44151 (Word) or by other means.
  • Information on communicable disease reporting
Wisconsin case reporting and public health follow-up guidelines

Case Reporting and Investigation Protocol (EpiNet): P-01879 Smallpox (PDF)

Questions about Smallpox? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976

Last revised October 7, 2021