Mpox mutates AGAIN - new variant is highly transmissible, experts warn
Published: 10:59 GMT, 5 March 2025
Health officials have sounded the alarm over a new mutant 'highly transmissible' mpox strain, believed to be behind a wave of fresh cases.
A newly discovered variant of the rash-causing virus is now spreading in the Democratic Republic of Congo (DRC), experts say.
It is a descendant of the deadlier clade 1a strain of mpox, formerly known as monkeypox, which is estimated to kill up to 10 per cent of patients — far more than other strains that have spread in recent months.
Officials are worried because the new version carries a mutation known as APOBEC3 which makes it more infectious than its predecessor.
Scientists say the same mutation has already been seen in the Clade 1b mpox strain, which has spread far beyond Africa to the UK, Europe and Asia within the last year.
Experts have warned that swift action from the international community is needed to help stop any potential larger mpox outbreak of the new variant outside of DRC.
Latest World Health Organisation (WHO) data shows more than 2,063 mpox cases have been logged in the nation in 2025 alone, including four deaths.
However, it is unclear exactly how many cases, and deaths, the new mutant Clade 1a strain accounts for, with older versions still circulating.
In a briefing Dr Ngashi Ngongo, head of the mpox incident management team at the Africa Centres for Disease Control and Prevention (Africa CDC), said: 'We have seen a new variant of Clade 1a with APOBEC3 that has been detected, and unlike the old 1a variant, this one has got high potential for higher transmissibility.'
The WHO also says: 'The current understanding is that Clade 1 leads to more severe disease and death than Clade 2 in the populations where it is endemic.'
Most Clade 1a infections have been linked to spillovers from animals, with limited human-to-human transmission in close-contact settings like households observed.
Clade 1a has a fatality rate ranging from 1.4 per cent to over 10 per cent, far more than the 0.1 per cent and 3.6 per cent recorded for Clade 2.
Research published in January in the New England Journal of Medicine, suggests the Clade 1b rate stands around 3.3 per cent.
But Dr Lorenzo Subissi, a virologist with the WHO Health Emergencies Programme, told The Telegraph that higher fatality rates haven't been observed, so far, with the new Clade 1a strain.
While this variant may spread outside of DRC, the mortality rate seen in Kinshasa, where the new Clade 1a variant co-circulates with Clade 1b, remains less than one per cent, so much lower than what was historically thought to be clade 1a mortality,' he said.
'Mortality will largely depend on underlying conditions of the affected population such as malnutrition.'