Monkeypox

Mpox is an infectious disease caused by the monkeypox virus (MPXV), an enveloped double-stranded DNA virus of the Orthopoxvirus genus, Poxviridae family, which also includes variola, vaccinia and cowpox viruses ^[1][2]. Two distinct clades of the virus circulate: clade I (with subclades Ia and Ib) and clade II (with subclades IIa and IIb) ^[1]. Following global expert consultation, WHO now uses "mpox" as a preferred synonym for monkeypox ^[3].

Common symptoms include a painful rash, enlarged lymph nodes, fever, headache, muscle ache, back pain and low energy; most patients fully recover, although some develop severe illness ^[1][5]. The rash typically begins on the face and spreads to the body including the palms and soles, but may start at sites of contact such as the genitals, progressing through macules, papules, vesicles and pustules before forming scabs over two to four weeks ^[5][4]. Symptoms usually begin within a week of exposure but can start 1–21 days afterwards, and lesions can leave scars ^[5][2]. Complications requiring medical attention have been reported in up to 40% of patients during the 2022 outbreak and include rectal pain, odynophagia, penile oedema, and skin and anorectal abscesses ^[2].

The first human case of mpox was detected in the Democratic Republic of the Congo in 1970, and the disease has since caused sporadic infections and outbreaks mainly restricted to some countries in west and central Africa ^[2]. A global outbreak of clade IIb MPXV spread to at least 118 countries, affected more than 99,000 persons worldwide, and resulted in a Public Health Emergency of International Concern (PHEIC) from July 2022 to May 2023, with over 33,000 infections and 60 deaths reported in the United States ^[4]. In 2024, the United States has recorded approximately 200 new infections per month, and on August 14, 2024, WHO declared mpox a PHEIC for a second time due to a rapid rise in clade I MPXV infections in Central Africa, with clade Ib subsequently detected beyond Africa ^[1][4]. Clade IIb MPXV is typically a self-limited illness with a case-fatality rate under 0.2% in the United States, while the case-fatality rate in the 2022 outbreak has been reported below 0.1% ^[4][2].

Person-to-person transmission occurs mainly through close contact with an infected individual, including skin-to-skin contact (such as touching or sex), mouth-to-mouth or mouth-to-skin contact (such as kissing), and face-to-face exposure that can generate infectious respiratory particles ^[3][1][5]. Transmission can also occur through exposure to bodily fluids, skin or mucosal lesions, respiratory particles, and contaminated objects such as clothing or linen, and has been documented through needle injuries in health care and in community settings such as tattoo parlours ^[1][5]. During the 2022 global outbreak, the virus spread predominantly through sexual contact, and the virus may also be transmitted during pregnancy or birth to the baby ^[1][4]. Zoonotic transmission can occur through bites, scratches, or activities such as hunting, skinning, trapping or preparing meat from infected animals, or through eating insufficiently cooked contaminated meat, with small mammals such as squirrels and monkeys being susceptible hosts in tropical rainforest areas of central, east and west Africa ^[3][1][5].

Mpox vaccination can prevent infection when administered before exposure and is recommended for people at high risk of infection, especially during outbreaks ^[1]. The vaccine can also be used after exposure as post-exposure prophylaxis and should ideally be given within four days of contact with a case, though it may still be administered up to 14 days if illness has not developed ^[1]. Reducing zoonotic risk involves avoiding unprotected contact with wild animals, especially those that are sick or dead (including their meat and blood), and ensuring that foods containing animal parts are cooked thoroughly ^[3][1]. Limiting sexual contact with multiple partners and avoiding close contact with individuals who have mpox are additional measures that reduce person-to-person transmission ^[1].

1. 1 World Health Organization. Mpox [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/mpox
2. 2 Mitjà O et al. Monkeypox. Lancet. 2023 Jan 7. PMID: 36403582. doi: 10.1016/S0140-6736(22)02075-X. PubMed: https://pubmed.ncbi.nlm.nih.gov/36403582/
3. 3 World Health Organization. Mpox [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/news-room/questions-and-answers/item/mpox
4. 4 Titanji BK et al. Mpox Clinical Presentation, Diagnostic Approaches, and Treatment Strategies: A Review. JAMA. 2024 Nov 19. PMID: 39401235. doi: 10.1001/jama.2024.21091. PubMed: https://pubmed.ncbi.nlm.nih.gov/39401235/
5. 5 World Health Organization. Mpox [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/health-topics/mpox