Study detects monkeypox virus in anal samples from asymptomatic individuals

A study at the Bichat-Claude Bernard Hospital in Paris, France, has detected monkeypox virus in anal samples from asymptomatic men who have sex with men (MSM).

These results suggest that vaccination limited to those with known exposure to monkeypox virus may not be sufficient to prevent infection, according to the study, published in the scientific journal ‘Annals of Internal Medicine’.

Researchers retrospectively tested for monkeypox virus with PCR on all anorectal swabs collected as part of a screening program for sexually transmitted infections.

According to French guidelines, this type of screening is performed every 3 months among MSM with multiple sexual partners taking HIV pre-exposure prophylaxis (PrEP) or living with HIV and receiving antiretroviral treatment.

Of the 200 asymptomatic persons tested who tested negative for ‘N. gonorrhoeae’ and ‘C. trachomatis’, 13 (6.5%) samples tested PCR positive for monkeypox virus. Two of the 13 individuals subsequently developed symptoms of monkeypox.

Whether asymptomatic infection plays a role in monkeypox virus transmission is unknown. But the current worldwide epidemic of monkeypox and the mode of human-to-human transmission may provide evidence that asymptomatic or preclinical spread may occur.

The researchers suggest that “an expanded strategy of ring vaccination and other public health interventions in the most at-risk communities is likely needed to help control the outbreak.”