Viral

Mpox (monkeypox)

A sexually transmissible viral infection that spreads in outbreaks — worth watching, but not something we put a number on.

Not in the calculator

Mpox is not in the calculator. It spreads in outbreaks within sexual networks rather than at a steady background rate, so a per-encounter percentage would be misleading. During an active outbreak in your area, treat any new genital, anal, or oral rash or sores as a reason to get checked — and to consider vaccination if you are eligible.

Cause

Virus (MPXV)

Spread

Close / skin-to-skin contact

Course

Usually self-limiting (2–4 weeks)

Vaccine

Yes — JYNNEOS, during outbreaks

Overview

Mpox (formerly monkeypox) is caused by the monkeypox virus (MPXV). Long endemic in parts of Central and West Africa, it caused a large global outbreak from 2022 that spread predominantly through close contact during sex, especially among gay, bisexual and other men who have sex with men. It is usually a self-limiting illness lasting 2–4 weeks, but can be severe in people who are immunocompromised, pregnant, or very young. Because outbreaks flare and subside rather than maintaining a steady population prevalence, this tool flags Mpox for awareness instead of estimating per-encounter risk.

How it spreads

Direct skin-to-skin or mucosal contact with mpox lesions during sex
Prolonged close face-to-face contact (respiratory droplets)
Contact with contaminated materials such as bedding, towels, or sex toys
From a pregnant person to the fetus

Symptoms

A rash or blisters, often on or around the genitals, anus, or mouth
Fever, headache, and muscle aches
Swollen lymph nodes (a distinctive feature)
Sore throat or painful rectal inflammation (proctitis)

Lesions may be few, small, or hidden (for example inside the anus or mouth), so the illness can be mistaken for another STI. A person is generally considered infectious from the onset of symptoms until all lesions have crusted, scabbed, and healed with fresh skin.

Vaccine

A vaccine (JYNNEOS / MVA-BN) is offered to people at higher risk during outbreaks and as post-exposure prophylaxis. Older smallpox vaccination also offers some cross-protection. Availability depends on local outbreak response.

Treatment

Most cases resolve on their own within 2–4 weeks with supportive care for pain and to prevent secondary infection. The antiviral tecovirimat may be considered for severe disease or high-risk patients. People with mpox are advised to isolate and avoid sexual contact until all lesions have fully healed.

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Educational purposes only. Consult a healthcare provider for personal medical advice.