Monkey smallpox: new research may help explain sexual transmission of the disease

A type of monkeypox virus circulating in Central Africa has gained the ability to transmit itself sexually, says research that has not yet been peer-reviewed. Through genomic analysis, the study identified a lineage of the virus distinct from that typically circulating in the region.

Until last year, this type of Monkeypox virus, called Clade I, was mainly contaminated by rodents. There were few cases in which transmission occurred through contact with other people and, even in these, contamination was not due to sexual intercourse.

The research was published this month on medRxiv, a website created by a Yale laboratory that publishes studies that have not yet been reviewed. Therefore, the conclusions of articles published on the platform should not yet be used to guide clinical practices or health-related behaviors.

In the article, the authors of the article point out the similarity of the evolution of Clade I with the type of virus that led to the explosion of monkeypox in the world in 2022.

Researchers collected surveillance data and hospital records in the Democratic Republic of Congo, located in Central Africa, between October 2023 and January 2024. Last year, an outbreak of monkeypox exploded in the Kamituga mining region located in Congo. The area is densely populated, with a population exceeding 240 thousand inhabitants.

Of the 241 suspected cases of monkeypox in the region, 108 were confirmed. Of these, 29% were related to sex workers, “highlighting sexual contact as a key mode of infection,” says the article.

Other evidence that points to contamination by sex is the age of the patients. In Kamituga, the majority of affected individuals were teenagers and young adults, which contrasts with other outbreaks of the disease in the Democratic Republic of Congo, where the majority of patients are children under 15 years of age.

Furthermore, hospital records indicated that the majority of suspected cases had genital lesions compatible with the virus.

The researchers state that there is evidence that the new strain probably already existed in the region, but contaminated non-human animals.

There are two types of monkeypox virus: that from West Africa, called Clade II, and that from the Congo Basin (Central Africa), called Clade I. One of the points in which the two types differ is the severity of the virus. illness. While Clade II mortality is 4%, Clade I mortality is 11%.

Historically, 95% of monkeypox cases were the responsibility of Clade I. But in 2017, a large Clade II outbreak emerged in Nigeria. Genomic analyzes suggest that the mutation that allowed human-to-human transmission, mainly sexually, appeared in 2015.

The virus that caused the 2022 monkeypox outbreaks and caused the World Health Organization to declare a global health emergency comes from West Africa. At the time, 90% of registered cases were transmitted through sexual contact.

Although Clade I viruses are not known to be transmitted between humans, a study published in 2023 in the journal Centers for Disease Control and Prevention recorded sexual transmission of this type for the first time.

Access the study at medRvix.