Mpox clade Ia has evolved to jump from humans to humans: new study Premium

Scientists monitor mpox virus mutations and human-to-human transmission, impacting vaccination strategies in Africa.

Since the world eradicated smallpox in 1980, scientists have known that the battle against poxviruses was far from over. Of the multiple types that exist, scientists have been wary of one in particular: mpox. In fact, one of the points in the World Health Assembly’s post-eradication policies was the “continuation of monkeypox surveillance in West and Central Africa, at least until 1985”.

In the 2022-2023, the World Health Organisation (WHO) declared the then global outbreak of mpox a ‘public health emergency of international concern’. In August this year, the WHO declared mpox to be a public health emergency for the second time in two years.

(Note: In 2022, the WHO designated “mpox” as a preferred synonym for “monkeypox” disease. The virus is still called “monkeypox” according to the International Committee on the Taxonomy of Viruses. For uniformity’s sake, this article will use “mpox” to refer to both the disease and the virus clades.)

The declaration ensured multiple countries would pledge vaccines to the 15 African nations affected by the outbreak, six of which had never reported a single case of mpox before. But the paucity of doses has forced countries to prioritise their campaigns. Barely two months since these countries started their targeted vaccinations, scientists have a new cause for worry. A preprint paper uploaded on Virologica, a scientists’ discussion forum online, on October 24 reported evidence that yet another strain of the mpox virus appeared to have achieved human-to-human transmission.

There are two clades of mpox: I and II. Clade I viruses have been shown to cause more severe disease in the mouse model, but that doesn’t mean the same may be true for humans. Both clades are classified into two subclades, making a total of four known variants: Ia, Ib, IIa, and IIb. Of these, clade IIb was responsible for the 2022 outbreak, which is still continuing in certain parts of Africa.

Clade Ib, discovered towards the end of 2023, is the primary cause of infection in central Africa.

Researchers believed these two clades to be the primary contributors of the present mpox problem. They know very little about clade IIa except that it causes infections in western Africa.