A brief report documented 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 – “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” by Valentine Marie Ferré, Antoine Bachelard, Meryem Zaidi, Laurence Armand-Lefevre, Diane Descamps, Charlotte Charpentier, and Jade Ghosn -was published in Annals of Internal Medicine.
The 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 three 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 suggested 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.