The UK Health Security Agency (UKHSA) has identified a new recombinant strain of mpox (formerly monkeypox) that contains elements of clade Ib and clade IIb of the virus, in a traveler who recently returned from Asia. In a paper describing the new strain, the researchers at UKHSA say it is not possible to determine from a single genome how long the recombinant virus has been in circulation, or whether it will have a fitness benefit over currently circulating lineages.