What’s new in understanding monkeypox clinical presentation and transmission risk

Reviewed by: Dr. Michael Payne, MD; London Health Sciences Centre

The global monkeypox outbreak continues and timely identification and isolation of cases are important components to preventing continued transmission. Suspect cases are identified based on a characteristic rash, systemic symptoms along with epidemiologic risk factors. However, cases during the current outbreak differ from the classic presentation. In particular, rectal pain/proctitis is common and there may a biphasic appearance of genital and disseminated lesions. As well, the timing of systemic symptoms in relation to lesion appearance vary. There is also evidence of asymptomatic infections, as diagnosed from asymptomatic rectal swabs. Health care providers must be aware of the common symptoms and receive training for the indicated additional precautions for suspect monkeypox cases. However, the risk of transmission to health care providers is low, based on current evidence.

A descriptive case series from the United Kingdom outlines the common clinical symptoms of 197 monkeypox infected patients. All patients were male, and 196 identified as gay, bisexual or other men who have sex with men. All patients had mucocutaneous lesions, most commonly on the genital or perianal area. The common systemic symptoms were fever (61.9%) and lymphadenopathy (57.9%), however 13.7% of patients presented with rash alone, without systemic symptoms. Rectal pain/proctitis was common, present in 36% of patients. Systemic symptoms preceded rash in 61.5% of patients, but followed after rash appearance in 38.5% of patients, which differs from the classic monkeypox presentation. Asymptomatic infections have been described in a retrospective case series from a French sexual health clinic. Patients who identified as men who have sex with men, retrospectively had their rectal swabs tested by monkeypox PCR. A total of 323 asymptomatic men were evaluated and 200 had rectal swabs available for testing, of these 13 (6.5%) had a positive monkeypox PCR result, with 2 of these patients subsequently presenting with symptoms. This study was performed during a high epidemiology period of monkeypox community transmission but does inform the rate of possible asymptomatic infections; however, the contribution of asymptomatic cases to community transmission is not known. Finally, a study from Colorado followed 313 health care providers (HCP) for 21 days after their exposure to monkeypox infected patients. Only 23% of HCP wore all the recommended PPE during their exposure, however, masking was common likely due to COVID-19 precautions. 87 HCP had high-intermediate exposures qualifying for post-exposure prophylaxis with vaccination, however, only 37 received PEP. No HCP acquired monkeypox infection. This study is reassuring regarding the risk of transmission for HCP caring for patients with monkeypox infections, but it does highlight the need for improved education and training for appropriate PPE/additional precautions for suspect/confirmed monkeypox cases.


Patel et al. Clinical features and novel presentations of human monkeypox in a central London centre during the 2022 outbreak: descriptive case series. BMJ. 2022 Jul 28;378:e072410. doi: 10.1136/bmj-2022-072410.

Marshall KE, Barton M, Nichols J, et al. Health Care Personnel Exposures to Subsequently Laboratory-Confirmed Monkeypox Patients — Colorado, 2022. MMWR Morb Mortal Wkly Rep 2022;71:1216–1219. DOI: http://dx.doi.org/10.15585/mmwr.mm7138e2.

Ferré VM et al. Detection of Monkeypox Virus in Anorectal Swabs From Asymptomatic Men Who Have Sex With Men in a Sexually Transmitted Infection Screening Program in Paris, France. Ann Intern Med. 2022 Aug 16. doi: 10.7326/M22-2183.

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