Mpox (formerly Monkeypox)

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

Credit

NIAID

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

Credit: NIAID

The monkeypox virus (mpxv) is part of the Orthopoxvirus genus, which also includes variola virus (the cause of smallpox), vaccinia virus, and cowpox virus. It causes mpox disease, formerly known as monkeypox disease. Although mpox is similar to smallpox, it is much less deadly. Initial symptoms of mpox 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 mpxv occurs through direct contact with body fluids, lesions, prolonged face-to-face contact, including sexual contact, and indirect contact with contaminated clothing or bedding. 

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 mpox was recorded in 1970 in the Democratic Republic of the Congo (DRC). The disease is endemic in central and western Africa.

2022 Outbreak

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

Mpxv virus variants are referred to as clades: Clade I (formerly known as the Congo Basin or Central African clade) and Clade II (formerly known as the West African clade). Clade II is further divided into subclades: Clade IIa and Clade IIb. According to the World Health Organization, cases identified as part of the ongoing global outbreak are largely caused by Clade IIb. Clade I is responsible for infections in the DRC and is estimated to cause more severe disease and higher mortality than Clades IIa and IIb.
 

NIAID Research Role

NIAID played a key role in the development of a currently available vaccine to prevent mpox and smallpox, as well as antiviral treatments for smallpox that may also be used for mpox. Additionally, NIAID provided diagnostic support during several mpox outbreaks in the Democratic Republic of Congo over a four-year period. Today, NIAID scientists continue to conduct research to better understand mpox transmission and disease. NIAID performs genomic sequencing to better understand mpxv, 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 mpox. 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 is conducting two clinical trials of the smallpox drug tecovirimat (TPOXX) as a treatment for patients with mpox. The NIAID-supported repositories, the BEI Resources Repository and World Reference Center for Emerging Viruses and Arboviruses supply viral isolates and reagents for distribution to global research and surveillance communities.