The viral loads of monkeypox were similar, regardless of whether people had symptoms or not.
The viral loads of monkeypox were similar, regardless of whether people had symptoms or not.
Smallpox is transmitted by close contact with people who have a symptomatic infection, and all infected people are thought to have symptoms. But a recent study has found that people can become infected with monkeypox without showing any of the typical or atypical symptoms. The prepress has been published in medrXiv server, which has not yet been peer-reviewed.
The study found that three men tested positive for monkeypox but showed no symptoms. “The three men denied having had any symptoms in the weeks before and after taking the sample. None of them reported exposure to a diagnosed case of monkeypox, nor did any of their contacts develop clinical smallpox. “, points out the prepress.
Assumed symptoms
Similar to smallpox, anyone who is infected with monkeypox is expected to develop symptoms and the virus is thought to spread through close contact with people with symptoms. Since every individual infected with monkeypox is assumed to have symptoms, and because close contact is often needed for the virus to spread, it is considered that staying away from infected people and maintaining simple hygienic measures can stop the infection. spread of monkeypox virus, as observed. in various outbreaks in endemic regions.
But asymptomatic transmission can change and challenge efforts to contain the monkeypox outbreak, which as of July 4 has been reported in 6,027 people in 59 countries, including those endemic to Africa.
According to the World Health Organization (WHO), “the extent to which asymptomatic infection can occur is unknown.”
Curious case of asymptomatic monkeypox infection
Smallpox is considered to be transmitted by close contact with people who have a symptomatic infection
But the study found that three men tested positive for monkeypox without any obvious symptoms
None of them reported exposure to a diagnosed case of monkeypox nor did any of their contacts develop clinical smallpox.
All three men had sex without a condom with at least one male partner between a few days and a month before sampling.
Cycle threshold (Ct) values in anorectal samples taken from asymptomatic men were similar to or lower than samples taken from typical monkeypox skin lesions.
Lower Ct values suggest that the anorectal mucosa of asymptomatic cases may be as infectious as the skin lesions of symptomatic cases.
No matter if people showed symptoms or not, viral loads were comparable
This supports the hypothesis that monkeypox virus can be transmitted through anal sex, even in the absence of symptoms.
Retrospective tests at a sexual health clinic in Belgium find three men positive for monkeypox but asymptomatic
The researchers retrospectively examined 224 clinical samples collected for sexually transmitted infections (gonorrhea or chlamydia) throughout May 2022 with a monkey-specific PCR of smallpox. And they found evidence of asymptomatic monkeypox virus infection in three individuals. They tested anorectal and / or oropharyngeal samples collected from 224 people at the HIV / STI clinic of the Institute of Tropical Medicine in Antwerp, Belgium.
The three men who tested positive for monkeypox were informed of their diagnosis and were recalled to the clinic for further investigation of the case and follow-up of contacts. Follow-up samples were collected from the three men when they were recalled to the clinic. Repeated samples collected 21-27 days later were all negative.
At the time they were removed to the clinic, none of them showed signs or symptoms of monkeypox and all denied having noticed any symptoms during the previous two months or three weeks after the initial sample, write the authors. All three men had sex without a condom with at least one male partner between a few days and a month before sampling.
The authors note that one of the three men who tested positive for monkeypox and was asymptomatic was prior to the first symptomatic case detected in Belgium for several days. There were no epidemiological links with any other cases of monkeypox, nor did it report international travel or participation in mass meetings.
“This may indicate that the monkeypox virus circulated among asymptomatic individuals in Belgium before the outbreak was detected,” they write.
The researchers also noted that cycle threshold (Ct) values in anorectal samples taken from asymptomatic men were “similar to or lower than those taken from skin lesions typical of monkeypox.” Based on the lower Ct values of the anorectal samples, the researchers note that “the anorectal mucosa of asymptomatic cases can be as infectious as the skin lesions of symptomatic cases.”
Similar viral loads
The anorectal cycle threshold values of symptomatic cases were in the same range as those with no symptoms. This, according to the authors, suggests similar viral loads irrelevant whether they showed symptoms or not. “This would support the hypothesis that the monkeypox virus can be transmitted through anal sex, even in the absence of symptoms,” they write.
They also add: “It is possible that in the current outbreak in non-endemic environments, the asymptomatic carrier plays a more important role in the transmission of the virus … In the current outbreak, the skin rash often remains localized at the site of the “Inoculation and mode of transmission appear to be sexual. In this case, the asymptomatic carrier, especially with high viral loads on the anal mucosa, could therefore be an important motor of transmission.”
Unnoticed skin lesions
Although they claim that virus transmission in the absence of noticeable symptoms could explain why self-isolation at the onset of symptoms has been insufficient to stop the epidemic so far, they warn that all three men may not have been completely free of symptoms at first presentation. when samples were collected. This is because then no clinical examination was done and then no symptoms were reported due to memory bias or because the small skin lesions went unnoticed.
But more studies are needed to confirm or refute the findings of these researchers. In the meantime, more efforts should be directed at identifying asymptomatic cases through greater contact tracking and screening of high-risk populations, they say.