Newer mpox strain poses bigger risk to young women, study shows

Girls and young women may be more susceptible to an infectious subvariant of the virus that causes mpox that has spread from the Democratic Republic of Congo to neighboring countries, a study showed.

Of 154 cases that tested positive for mpox in Burundi, which borders eastern Congo, from July 3 to Sept. 9 the median age was 9.5 years, researchers said in a study released Oct. 17 in the scientific journal Eurosurveillance. The average age of girls who were infected was six years old, while boys were 17.5 years old, the data showed.

The subvariant, clade Ib, appears to spread more rapidly than an earlier variant, with hundreds of children having died of the disease in eastern Congo. The newer strain has been spreading through close physical contact as well as sexual activity of all kinds.

That compares to clade Ia, which has been circulating for decades in central and west Africa, but is mainly transmitted through contact with animals. Clade II, which has spread worldwide, is primarily transmitted through sexual intercourse between men.

Gender-specific differences were present “when considering age, mpox positivity and hospitalization,” the researchers wrote. There was little difference in age between males and females who tested negative among suspected cases, they said.

A separate analysis of 254 patients in the teaching hospital in Bujumbura, Burundi’s biggest city, showed a stark difference between men and women. Females who were hospitalized with the disease were on average 16 years old compared with men, who were 32 years old.

Most people who were hospitalized had a general pustular rash and 20% had a genital rash. While half had fevers and more than a third had swollen lymph glands, there were a few instances of muscle pains and two cases of loss of vision.

Prior to the current outbreak of clade Ib, Burundi hadn’t reported any cases of mpox. No related deaths have been recorded in the country, even as 1,100 Africans have died this year from disease caused by all variants of the virus, according to the Africa Centers for Disease Control and Prevention.

Researchers who worked on the study were from universities in Canada, Belgium, Burundi, Congo and the U.S.

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