Is Smallpox and Monkeypox Contagious?

Updated August 13, 2022


When smallpox was circulating in the environment, it was contagious; however, transmission generally required extended face-to-face contact with an infected person. It was also transmitted through respiratory droplets when an infected individual sneezed or coughed. Rarely, the virus was spread through airborne transmission. This meant that the virus could have remained in the air for an extended period of time and possibly even circulated throughout a building’s ventilation system. Coming into contact with scabs or the fluid (pus) contained in the smallpox rash pustules or bedding and clothing that has come into contact with scabs or fluid can also cause smallpox infection.1 2 Smallpox is only contagious to humans and there is no evidence that the virus can be spread to other species or to insects.3

Smallpox was declared extinct in May 1980 by the World Health Organization (WHO). There are, however, two known stores of smallpox virus remaining. One is located in the U.S. at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia and the other in a laboratory outside of Moscow, Russia. Some government health officials believe that secret smallpox stores exist and could someday be used for bioterrorism.4

Monkeypox virus is considered to be closely related to the smallpox virus5 and is contagious. The virus can be transmitted from animals to humans by scratches or bites, through direct contact with the rash lesions or other bodily fluids, or through meat from contaminated animals. Infected humans can spread the virus to others through respiratory secretions or other bodily fluids. Direct contact with the lesions or contact with items contaminated by the lesions such as clothing or linen can also transmit the infection.6 The virus can also be transmitted sexually.7

The last known case of smallpox reportedly occurred in Somalia in October 1977. In May 1980, smallpox was declared extinct by the World Health Organization (WHO). There are two known smallpox virus stores remaining. One is located in the U.S. at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia and the other in a laboratory outside of Moscow, Russia. Some government health officials believe that secret smallpox stores exist and could someday be used for bioterrorism.8

IMPORTANT NOTE: NVIC encourages you to become fully informed about smallpox and the smallpox vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself. This information is for educational purposes only and is not intended as medical advice.


References:

[1] Mayo Clinic. Smallpox. In: Symptoms & causes. Sept. 22, 2020.

[2] U.S. Centers for Disease Control and Prevention. Transmission. In: Smallpox. June 7, 2016.

[3] U.S. Centers for Disease Control and Prevention. Transmission. In: Smallpox. June 7, 2016.

[4] National Organization for Rare Disorders. Smallpox. In: Rare Disease Database. 2009.

[5] U.S. Centers for Disease Control and Prevention. Vaccine Effectiveness. In: Monkeypox. June 2, 2022.

[6] U.S. Centers for Disease Control and Prevention. Transmission. In: Monkeypox and Smallpox Vaccine Guidance. July 16, 2021.

[7] World Health Organization Regional Office for Europe. Monkeypox cases reported in the WHO European Region. May 20, 2022.

[8] National Organization for Rare Disorders. Smallpox. In: Rare Disease Database. 2009.

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