image of monkeypox virus
Colorized scanning electron micrograph of monkeypox virus (orange) on the surface of infected VERO E6 cells (green).

Colorized scanning electron micrograph of monkeypox virus (orange) on the surface of infected VERO E6 cells (green).

Credit: NIAID

The monkeypox virus is part of the Orthopoxvirus genus, which also includes variola virus (the cause of smallpox), vaccinia virus, and cowpox virus. Although monkeypox is similar to smallpox, it is much less deadly. Initial symptoms of monkeypox infection include: fever, headache and body aches, fatigue, and swollen lymph nodes, followed by a rash of lesions on the skin. Human-to-human transmission of monkeypox occurs through direct contact with body fluids, lesions, prolonged face-to-face contact, and indirect contact with contaminated clothing or bedding. Animal-to-human transmission can occur through a bite or scratch, preparation of wild game, or direct or indirect contact with body fluids or lesions.

The virus was first discovered in 1958 in two outbreaks of a pox-like disease among colonies of research monkeys. The first human case of monkeypox was recorded in 1970 in the Democratic Republic of the Congo (DRC), where the majority of human monkeypox infections have occurred. The disease is endemic in central and western Africa, and infections linked to international travel or imported animals have occurred in Israel, Singapore, the United Kingdom, and the United States.

In 2022, an outbreak of cases began occurring in multiple countries where monkeypox had not normally occurred, including the United States. Early data suggest that gay, bisexual, and other men who have sex with men comprised a high number of those cases; however, anyone who has been in close contact with someone who has monkeypox is at risk for infection.

Why is the Study of Monkeypox a Priority for NIAID?

Monkeypox, like other pox viruses, is classified as a category A pathogen, which are those organisms/biological agents that pose the highest risk to national security and public health because they can be easily disseminated or transmitted from person-to-person, result in high mortality rates, have the potential for major public health impact, might cause public panic and social disruption, and require special action for public health preparedness. Although monkeypox is not as deadly as smallpox, it has a reported fatality rate between 1 and 11 percent. Cases may be severe, especially in children, pregnant women, or people with suppressed immune systems. Additionally, the lesions caused by monkeypox may lead to permanent scars.

How is NIAID Addressing This Critical Topic?

NIAID played a key role in the development of a currently available vaccine to prevent monkeypox virus disease and smallpox, as well as antiviral treatments for smallpox that may also be used for monkeypox. Additionally, NIAID provided diagnostic support during several monkeypox outbreaks in the Democratic Republic of Congo over a four-year period. Today, NIAID scientists continue to conduct research to better understand monkeypox transmission and disease. NIAID performs genomic sequencing to better understand the monkeypox virus and its strains, as well as ecological studies to understand spillover events. Investigators with NIAID’s Centers for Research in Emerging Infectious Diseases, located in endemic countries in Africa, are screening animals and humans for monkeypox. NIAID is also working to develop high-throughput diagnostics capable of determining history of infection and distinguishing between individuals who have been infected with a poxvirus and those who were vaccinated against smallpox. NIAID and its partners screen novel compounds in a search for potential antiviral candidate treatments and is working toward larger clinical testing for the smallpox drug tecovirimat (TPOXX) as a treatment for patients with monkeypox virus disease. The NIAID-supported repositories, the BEI Resources Repository and World Reference Center for Emerging Viruses and Arboviruses supply monkeypox viral isolates and reagents for distribution to global research and surveillance communities. 

For more information about monkeypox, see NIH Medline Plus


Currently, there is no specific treatment approved for monkeypox virus infection. However, there are antiviral medications that can be used to treat smallpox and other conditions that may help patients with monkeypox infection. NIAID supported the development of two of these smallpox treatments—tecovirimat or ST-246 (TPOXX), made by SIGA Technologies, New York, and brincidofovir (Tembexa), manufactured by Chimerix, based in Durham, N.C. NIAID is screening other novel compounds to find potential antiviral candidates to treat monkeypox and is working to conduct larger clinical testing of tecovirimat specifically to treat patients with monkeypox virus disease.

Read more about monkeypox treatment


NIAID provided significant support in the development of the JYNNEOS™ (also known as Imvamune or Imvanex) vaccine to prevent monkeypox and smallpox. The vaccine was developed for people with weakened immune systems who were at risk for severe side effects from the existing smallpox vaccines. The JYNNEOS vaccine is an attenuated (weakened) live virus vaccine approved by the U.S. Food and Drug Administration in 2019 for individuals at high risk for smallpox or monkeypox infection.

Read more about monkeypox vaccines
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