The Sneak Attack of Monkeypox: 2 Studies Suggest Asymptomatic Spread of Infection Possible

Monkeypox disease has started hinting at the asymptomatic spread of infection that may impact the magnitude of the outbreak, two latest studies suggest.

The findings from a retrospective study conducted in Belgium show that certain cases of monkeypox remain undiagnosed and asymptomatic. It suggests that testing and quarantining of individuals reporting symptoms may not be sufficient to contain the outbreak.

The other study in France points out that the practice of “ring postexposure” vaccination around symptomatic persons with probable or confirmed monkeypox infection may not be sufficient to contain the spread.

Under the ring postexposure strategy, if a person is exposed to a virus, a vaccine is given to others who are in close contact with that person, such as close family and friends.

According to the experts, the findings reiterate the need for high-alert, surveillance, and strategies for the assessment of risk and prevention against the outbreak.

First study

Findings published in the medical journal Nature, titled “Restrospective detection of asymptomatic monkeypox virus infections among male sexual health clinic attendees in Belgium”, suggest “a lack of recognised, clinical symptoms could play a role in virus transmission and the magnitude of the 2020 monkeypox virus outbreak”.

“The magnitude of the 2022 multi-country monkeypox virus outbreak has surpassed any preceding outbreak. It is unclear whether asymptomatic or otherwise undiagnosed infections are fuelling this epidemic,” said the article published on August 12.

The article aimed to assess whether undiagnosed infections occurred among men attending a Belgian sexual health clinic in May 2022. Authors retrospectively screened 224 samples collected for two other diseases – gonorrhoea and chlamydia – using a monkeypox virus PCR assay, and identified monkeypox DNA-positive samples from four men.

“At the time of sampling, one man had a painful rash, and three men had reported no symptoms. Upon clinical examination 21 to 37 days later, these three men were free of clinical signs and they reported not having experienced any symptoms. These findings show that certain cases of monkeypox remain undiagnosed, and suggest that testing and quarantining of individuals reporting symptoms may not suffice to contain the outbreak,” says the article.

Second study

Another report from France was published in the journal Annals of Internal Medicine on August 16. The study aimed to assess the presence of the monkeypox virus in samples among asymptomatic MSM (men who have sex with men) routinely tested for bacterial sexually transmitted infections.

706 men visited the Infectious Disease Department and the Sexual Health Clinic of Bichat-Claude Bernard Hospital in Paris, France, from June 5 to July 11, 2022. Out of 706 men, 383 had symptoms suggestive of monkeypox infection, and the infection was confirmed in 271 of those with symptoms.

“Of the 187 asymptomatic participants who tested negative for the virus, 3 presented to our clinic more than 3 weeks after the initial monkeypox-negative anal swab with symptoms suggestive of monkeypox infection and tested positive,” the report said.

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