New Mpox Variant Sparks Concern As Experts Warn of High Transmissibility

The new strain, a descendant of the more lethal Clade 1a variant, has been detected in the DRC, according to experts. Clade 1a, previously known as monkeypox, has an estimated fatality rate of up to 10%, significantly higher than other recent variants.

Officials express concern as the emerging strain carries the APOBEC3 mutation, which enhances its infectious potential. This mutation has also been observed in the Clade 1b strain, which has spread beyond Africa to the UK, Europe, and Asia over the past year.

Health experts are calling for swift international action to contain the new variant’s potential spread. According to the latest World Health Organization (WHO) data, the DRC has recorded over 2,063 mpox cases in 2025, including four deaths. However, it remains unclear how many of these cases stem from the newly mutated Clade 1a strain, as older variants continue to circulate.

"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," said Dr. Ngashi Ngongo, head of the mpox incident management team at the Africa Centres for Disease Control and Prevention (Africa CDC), during a briefing.

The WHO notes that Clade 1 strains generally cause more severe illness and higher mortality rates than Clade 2. Historically, Clade 1a infections have been linked to zoonotic spillover events, with limited human-to-human transmission occurring primarily in close-contact settings. Fatality rates for Clade 1a range from 1.4% to over 10%, whereas Clade 2 mortality rates vary between 0.1% and 3.6%. A study published in January in the New England Journal of Medicine estimates Clade 1b’s fatality rate at approximately 3.3%.

Despite concerns over its transmissibility, there is no current evidence suggesting increased mortality associated 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 percent—much lower than previously thought for Clade 1a," said Dr. Lorenzo Subissi, a virologist with the WHO Health Emergencies Programme. He added that mortality rates will depend largely on underlying health conditions such as malnutrition.

The discovery of the new strain coincides with the WHO’s decision to extend its declaration of the ongoing mpox epidemic as a public health emergency of international concern. The classification, first issued last August amid rising Clade 1b cases, remains in place due to increasing case numbers, geographic spread, armed conflict in eastern DRC that hampers response efforts, and insufficient funding.

Outbreaks in Africa primarily involve Clade 1a and 1b, with Clade 2 transmission remaining limited. Dr. Ngongo noted that several African countries continue to report rising mpox cases, while escalating violence in the DRC exacerbates the risk of further spread.

Beyond Africa, Clade 1b has been identified in countries including the UK, US, Sweden, Thailand, India, and Germany. The UK Health Security Agency has reported nine cases but maintains that the risk to the UK population remains low.

Since the outbreak began, mpox has caused at least 1,000 deaths in central Africa. The virus presents with fever, body aches, fatigue, and distinctive skin lesions. In severe cases, it can spread to the bloodstream, lungs, and other organs, leading to life-threatening complications.