New mpox clade 1 lineage identified in DR Congo outbreak

In a preprint study this week, a genetic sequencing analysis from an international group of researchers led by scientists in Africa identified a distinct mpox clade, fueling a severe outbreak in the Democratic Republic of the Congo (DRC). They proposed that the clade be named clade 1b and warned that urgent measures are needed to contain it due to its pandemic potential. 

The DRC's mpox outbreak has been under way since 2023 due to the clade 1 virus, which is different from the clade 2 virus that has spread globally, mainly in men who have sex with men, since 2022. The clade 1 virus is more virulent and deadlier than clade 2, and the DRC's outbreak has involved sexual spread and a high burden in children, who are contracting the virus from household contacts and small mammals.

Lineage may have come from animals

For the sequencing study, the team examined surveillance data and hospital records collected from October 2023 to January 2024. They evaluated diagnostic testing results from blood samples and oropharyngeal swabs, then sequenced and analyzed the virus genomes.

They noted that the outbreak spread rapidly from a mining area near Kamituga, with sex workers making up nearly 30% of lab-confirmed case-patients. Genetic analysis revealed a distinct clade 1 mpox virus that was different from earlier viruses that had been identified in the DRC. Mutations suggested the virus new clade emerged in September 2023 and spread person-to-person.

Analysis of gene sequences of earlier mpox cases in the outbreak areas suggested that the new lineage may have been present in in a local animal reservoir.

Call for swift action

The researchers said sustained spread in the Kamituga region raises concerns because of its poor healthcare infrastructure, frequent population travel to Rwanda and Burundi, and the fact that a number of the sex workers in Kamituga are foreigners and frequently return to their home countries.

So far, no cases involving the new lineage have been reported outside of the DRC. The group warned, however, "Given the recent history of mpox outbreaks in DRC, we advocate for swift action by endemic countries and the international community to avert another global mpox outbreak."