Will Asymptomatic Monkeypox Infections Cause Wider Spread?

Wednesday August 17, 2022

Will Asymptomatic Monkeypox Infections Cause Wider Spread?
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Can monkeypox be spread asymptomatically? A French study released this week suggests that could be the case, reports the Annals of Internal Medicine.

"Lab tests on anal samples from asymptomatic French men who were sampled regularly for other surveillance purposes were positive for monkeypox for some patients, suggesting that vaccination of only known contacts may not be enough to prevent spread of the virus," writes a summary of the report, published by the University of Minnesota's Center for Infectious Disease and Policy.

The French study was done by researchers from Bichat-Claude Bernard Hospital in Paris. They conducted monkeypox tests on anorectal swabs that were collected as part of routine sexually transmitted infection (STI) screening in men who have sex with men (MSM), have multiple sexual partners, and are on HIV preexposure prophylaxis or treatment. The samples were collected between Jun 5 and Jul 11.

"Of 200 asymptomatic people who were screened and were negative for two STIs, 13 (6.5%) were positive for monkeypox. Two of them developed monkeypox symptoms later," wrote the summary.

"The authors said it's not clear if viral shedding can lead to transmission. If so, they wrote that postexposure ring vaccination around people with probable or confirmed infections might not be enough to contain the spread of the virus."

In an editorial on the study, Stuart Isaacs, MD, with the division of infectious diseases at Perelman School of Medicine at the University of Pennsylvania, wrote though it's not clear if the positive polymerase chain reaction (PCR) results signify infectious virus, it wouldn't be surprising if it did, because asymptomatic infections aren't a new finding.

"However, it raises the question of whether asymptomatic or subclinical infections are contributing to the current worldwide outbreak," he wrote.

He emphasized that control will be successful only if vaccination is used alongside other tools such as identifying and isolating cases, making treatments available, and educating the public about ways to reduce exposure risk.