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
Background:
An outbreak of monkeypox virus (MPXV) emerged in May 2022, primarily affecting men who have sex with men (MSM). Although most infections were characterized by skin lesions, a recent report described 3 asymptomatic men without skin lesions but with positive MPXV anorectal polymerase chain reaction (PCR) test results (1). Determining whether MPXV infection can be asymptomatic may better inform epidemic management.
Aim :
To evaluate the presence of MPXV in anorectal samples among asymptomatic MSM undergoing routine testing for sexually transmitted bacterial infections (2).
Methods and findings:
We retrospectively performed MPXV testing on all anorectal swabs that were collected at our center as part of a screening program for Neisseria gonorrhoeae and Chlamydia trachomatis. According to French guidelines, this screening is performed every 3 months among MSM with multiple sexual partners who are taking HIV pre-exposure prophylaxis (PrEP) or living with HIV and receiving antiretroviral treatment. Patients can obtain urine samples and anal swabs at our clinic or at a private laboratory.
After the first case of MPXV infection was identified in France on May 19, 2022, screening was discontinued in patients presenting with lesions suspicious for MPXV (3). We report on asymptomatic MSM who tested negative for N gonorrhoeae and C trachomatis in MPXV anal swabs collected at the Department of Infectious Diseases and the Sexual Health Clinic of the Bichat-Claude Bernard Hospital in Paris, France, from June 5 to July 11, 2022.
All participants attended a clinic visit on the day of sampling as part of routine PrEP or HIV treatment follow-up. Participants gave written informed consent to have their data recorded in Nadis, an electronic medical record designed for the monitoring of people living with HIV or receiving PrEP for HIV, and the use of their data for research. The local review board did not require specific consent to use remaining routine biological samples in the context of the MPXV epidemic.
Of the 187 asymptomatic participants who tested negative for MPXV, 3 presented to our clinic more than 3 weeks after the initial negative MPXV anal swab with symptoms suggestive of MPXV infection and tested positive .
Discussion:
This report documents positive MPXV PCR results from anal specimens in asymptomatic MSM. It is unknown whether this indicates viral shedding that can lead to transmission. If so, the practice of post-exposure vaccination around symptomatic persons with probable or confirmed MPXV infection may not be sufficient to contain the spread. Recent French recommendations advise vaccination of all MSM with multiple partners.
Comments
A brief research report documents positive PCR results for monkeypox virus found in anal swabs taken from asymptomatic MSM (men who have sex with men). These findings suggest that vaccination limited to those with known exposure to monkeypox virus may not be an effective strategy to prevent infection. The report is published in Annals of Internal Medicine .
Researchers at Bichat-Claude Bernard Hospital, Paris, France, performed retrospective testing for monkeypox virus on all anorectal swabs that were collected as part of a sexually transmitted infection screening program. According to French guidelines, this type of screening is performed every 3 months among MSM with multiple sexual partners who are taking HIV pre-exposure prophylaxis (PrEP) or who are living with HIV and receiving antiretroviral treatment.
Of the 200 asymptomatic individuals tested who tested negative for N. gonorrhoeae and C. trachomatis, 13 (6.5%) samples tested positive by PCR for monkeypox virus. Two of the 13 later developed symptoms of monkeypox.
It is not known whether or not asymptomatic infection will play a role in the transmission of monkeypox virus. But the current global monkeypox epidemic and the person-to-person mode of transmission may provide evidence that asymptomatic or preclinical spread can occur. The author of an accompanying editorial suggests that the role of an expanded ring vaccination strategy and other public health interventions in higher-risk communities is likely needed to help control the outbreak.
