Mpox is caused by the monkeypox virus (MPXV). 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 affecting the skin and often mouth or genital area. Human-to-human transmission of the virus occurs through direct contact with lesions or body fluids, prolonged close contact including sexual contact, and indirect contact with contaminated clothing or bedding.
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. Two types of the virus that causes mpox have been identified. Clade I is endemic in Central Africa and can cause severe illness. Clade II, historically endemic in West Africa, tends to result in milder illness. People with compromised immune systems, children, and people who are pregnant are especially vulnerable to severe mpox regardless of the virus clade.
NIAID is conducting and supporting research focused on developing and evaluating treatments and vaccines for mpox, understanding disease pathogenesis, transmission, and spillover, evaluating immunological responses to MPXV, and bolstering the critical research resources foundational to supporting the ongoing public health response.
Editorial Note: The term “monkeypox” was previously used to describe the clinical disease caused by MPXV. The term “mpox” is preferred and now widely adopted because it is less stigmatizing. The virus that causes mpox is still classified as monkeypox virus (MPXV) by the International Committee on Taxonomy of Viruses.
Page Summary
Mpox is caused by the monkeypox virus (MPXV). MPXV is part of the Orthopoxvirus genus, which also includes variola virus (the cause of smallpox), vaccinia virus, and cowpox virus. NIAID is conducting and supporting research focused on developing and evaluating treatments and vaccines for mpox, understanding disease pathogenesis, transmission, and spillover, evaluating immunological responses to MPXV, and bolstering the critical research resources foundational to supporting the ongoing public health response.
