Mpox and sexual contact

What it is

Mpox (formerly monkeypox) is a viral illness caused by an orthopoxvirus related to smallpox. It has been endemic in parts of Central and West Africa for decades. A global outbreak beginning in May 2022 spread to over 100 countries, with more than 90,000 confirmed cases, and was driven predominantly by close sexual contact within sexual networks of men who have sex with men. A separate clade I outbreak centred on the Democratic Republic of the Congo and neighbouring countries prompted a further WHO public health emergency declaration in 2024.

Transmission

Close, sustained skin-to-skin contact, including sexual contact. Also through contact with lesion material, respiratory droplets during prolonged face-to-face contact, and contaminated bedding or towels. Viral DNA has been detected in semen, though the significance of that for transmission is not fully established.

It is not classified as a sexually transmitted infection in the conventional sense, because it does not require sexual contact — but in the 2022 outbreak, sexual contact was the dominant route. That distinction matters for accuracy and for avoiding both complacency and misdirected stigma.

Symptoms

Incubation is typically 5–21 days. The 2022–24 outbreak presented differently from classic descriptions:

• Lesions frequently began in the anogenital area or mouth, sometimes as a single lesion.
• Proctitis — severe rectal pain — was common and was often the presenting complaint.
• Lesions could appear before or without the fever and prodromal illness described in older literature.
• Some cases had very few lesions and were easily mistaken for herpes, syphilis or an ingrown hair.

Illness usually lasts 2–4 weeks and most people recover without specific treatment. It can be severe, particularly in people with advanced untreated HIV, in whom mortality in the 2022 outbreak was substantially elevated. Pain from anogenital and oral lesions is frequently severe enough to require significant analgesia.

A person is infectious

From symptom onset until all lesions have crusted, scabbed and new skin has formed underneath. That is typically 2–4 weeks. Isolation advice for this period is the standard containment measure, alongside covering lesions and avoiding sexual contact.

Vaccination

The MVA-BN vaccine (Jynneos, Imvanex, Imvamune) is a non-replicating modified vaccinia vaccine. Observational effectiveness studies from the 2022 outbreak found substantial protection — estimates around 66–86 percent after two doses, with meaningful protection after one. Two doses at least 28 days apart. Post-exposure vaccination within four days of exposure may prevent disease and within 14 days may reduce severity.

It is offered in most countries to men who have sex with men with multiple partners, to sex workers, to some healthcare and laboratory workers, and to close contacts of cases. Uptake and eligibility criteria vary widely.

Treatment

Mostly supportive: analgesia, which frequently needs to be substantial for proctitis and oral lesions, plus wound care and treatment of secondary bacterial infection. Tecovirimat is available in some settings, though the PALM007 trial in the DRC (2024) did not show a reduction in lesion resolution time, so its role is now more uncertain than initially assumed.

What to do

If you have unexplained anogenital or oral lesions, rectal pain, or a new rash after close contact: contact a sexual health service, tell them before attending so they can arrange the appointment appropriately, avoid sexual contact until assessed, and cover lesions. Testing is a swab of a lesion.

Stigma directly harmed the 2022 response by discouraging testing. Mpox is an infection transmitted by close contact, and the affected communities' rapid behavioural response and high vaccine uptake were the main reasons the outbreak was contained.

Sources

• Thornhill JP et al. "Monkeypox virus infection in humans across 16 countries — April–June 2022." NEJM, 2022.
• WHO. Mpox situation reports, and public health emergency declarations 2022 and 2024.
• Deputy NP et al. "Vaccine effectiveness of JYNNEOS against mpox disease in the United States." NEJM, 2023.
• UKHSA. Mpox clinical management and vaccination guidance, current edition.
• Mitjà O et al. "Mpox in people with advanced HIV infection: a global case series." Lancet, 2023.
• PALM007 trial results on tecovirimat, NIAID, 2024.

Last reviewed: August 2026.