Clade 1b Mpox: Higher Transmission, Elevated Miscarriage Concerns

A newly emerging variant of Mpox, Clade 1b, has been identified as highly infectious and linked to an increased risk of miscarriage, according to a study led by an international team of researchers. The variant, first detected in Kamituga, Democratic Republic of the Congo (DRC) in September 2023, has since undergone mutations that enhance its human-to-human transmissibility (1^✔ ✔Trusted Source
Epidemiological and genomic evolution of the ongoing outbreak of clade Ib mpox virus in the eastern Democratic Republic of the Congo

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Mpox Clade 1b: Global Spread and Subvariant Evolution Revealed

Published in Nature Medicine, the study reveals that Clade 1b has evolved into three subvariants, one of which has spread beyond Kamituga to other cities in the DRC, neighboring African nations, and even internationally to Sweden and Thailand. The variant has also been reported in the United States, where four cases have been detected since November 2023.

The research, conducted by experts from six countries including DRC, Denmark, the UK, and Spain, raises concerns about the virus’s impact on pregnant women. Among the 670 patient samples analyzed, 52.4% were women, with eight out of 14 pregnant patients suffering miscarriages. The study also recorded seven fatalities and noted that while sexual contact was the primary mode of transmission, three cases involved healthcare workers.

“For Clade 1b, we see that one particular subvariant appears to have become better at transmitting between humans, and it has now been detected in several countries outside East Africa. In addition, the number of infected pregnant women who miscarry is high,” said Professor Frank Moller Aarestrup from the DTU National Food Institute in Denmark.

Mpox was historically considered a zoonotic disease, primarily transmitted from animals to humans. However, the 2022 outbreak primarily affected men who have sex with men. In contrast, Clade 1b is infecting both men and women, with increasing cases among healthcare workers and children.

While Aarestrup noted that a large-scale outbreak beyond East Africa is not expected at this stage, the researchers stress the need for preventive measures. They recommend minimizing close contact, particularly sexual contact, in high-risk regions, strengthening international cooperation to track disease transmission, and increasing health education efforts, especially among vulnerable populations such as sex workers.

Reference:

1. Epidemiological and genomic evolution of the ongoing outbreak of clade Ib mpox virus in the eastern Democratic Republic of the Congo - (https://www.nature.com/articles/s41591-025-03582-1)

Source-Eurekalert