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Asymptomatic Monkeypox Virus Infections Among Male Sexual Health Clinic Attendees in Belgium
16 Pages Posted: 21 Jun 2022More...
Background: Monkeypox is transmitted by close contact with symptomatic cases, and those infected are assumed to be uniformly symptomatic. Evidence of subclinical monkeypox infection is limited to a few immunological studies which found evidence of immunity against orthopoxviruses in asymptomatic individuals who were exposed to monkeypox cases. We aimed to assess whether asymptomatic infections occurred among individuals who underwent sexually transmitted infection (STI) screening in a large Belgian STI clinic around the start of the 2022 monkeypox epidemic in Belgium.
Methods: Anorectal and oropharyngeal swabs collected for gonorrhoea/chlamydia screening from May 1 until May 31, 2022 were retrospectively tested by a monkeypox-specific PCR. Cases with a positive PCR result were recalled to the clinic for case investigation, repeat testing and contact tracing.
Findings: In stored samples from 224 men, we identified three cases with a positive anorectal monkeypox PCR. All three men denied having had any symptoms in the weeks before and after the sample was taken. None of them reported exposure to a diagnosed monkeypox case, nor did any of their contacts develop clinical monkeypox. Follow-up samples were taken 21 to 37 days after the initial sample, by which time the monkeypox-specific PCR was negative, likely as a consequence of spontaneous clearance of the infection.
Interpretation: The existence of asymptomatic monkeypox infection indicates that the virus might be transmitted to close contacts in the absence of symptoms. Our findings suggest that identification and isolation of symptomatic individuals may not suffice to contain the outbreak.
Funding Information: No external funding.
Declaration of Interests: No conflicts of interest to declare.
Ethics Approval Statement: The study protocol was approved by the Institutional Review Board of the Institute of Tropical Medicine (1600/22). Written informed consent is available from all asymptomatic cases.
Keywords: Monkeypox virus, asymptomatic, subclinical, transmission, infectiousness, epidemic
Suggested Citation: Suggested Citation