Report documents the detection of monkeypox virus in anal samples taken from asymptomatic MSM

Reviewed by Emily Henderson, B.Sc.Aug 16 2022

A brief research report documents positive monkeypox virus PCR results found in anal samples taken from asymptomatic MSM (men who have sex with men). These findings suggest that vaccination limited to those with known exposure to the monkeypox virus may not be an effective strategy for preventing infection. The report is published in Annals of Internal Medicine.

Researchers from Bichat–Claude Bernard Hospital, Paris, France, retrospectively performed testing for monkeypox virus on all anorectal swabs that were collected as part of a sexually transmitted infection screening program. Per French guidelines, this type of screening is performed every 3 months among MSM with multiple sexual partners who are either taking HIV preexposure prophylaxis (PrEP) or living with HIV and receiving antiretroviral treatment. Of the 200 asymptomatic persons screened that were negative for N. gonorrhoeae and C. trachomatis, 13 (6.5%) samples were PCR positive for monkeypox virus. Two of the 13 later developed symptoms of monkeypox.

Whether or not asymptomatic infection will play a role in transmission of monkeypox virus is not known. But the current worldwide monkeypox epidemic and the mode of human-to-human transmission may provide evidence that asymptomatic or preclinical spread can occur. The author of an accompanying editorial suggest that the role of an expanded ring vaccination strategy and other public health interventions in the communities at highest risk is likely needed to help control the outbreak.