The World Health Organization (WHO) has declared a global public health emergency in response to an mpox outbreak in Central Africa and the spread of a highly infectious new strain first detected in the Democratic Republic of Congo (DRC).

Mpox, formerly known as monkeypox, is a viral disease that spreads easily between infected people and animals. It can spread through sexual activity and contaminated materials, according to WHO.

WHO convened its emergency committee amid fear that a deadlier strain of the virus, clade Ib, had reached four previously unaffected countries in Africa after initially being contained to the DRC.

Independent experts met virtually on Wednesday (August 14) to advise WHO Director-General Tedros Adhanom Ghebreyesus on the severity of the outbreak. He then announced that a public health emergency of international concern [PHEIC] — the highest level of alarm under international health law.

“The detection and rapid spread of a new clade of mpox in eastern DRC, its detection in neighbouring countries that had not previously reported mpox and the potential for further spread within Africa and beyond is very worrying,” he said.

“The emergency committee met and advised me that the situation constitutes a public health emergency of international concern. I have accepted that advice.”

In the past month, over 100 laboratory-confirmed cases of clade 1b have been reported in four countries neighbouring the DRC that have not reported mpox before: Burundi, Kenya, Rwanda and Uganda. Experts believe the true number of cases to be higher as a large proportion of clinically compatible cases have not been tested, WHO said.

The Africa Centres for Disease Control and Prevention (Africa CDC) had declared the outbreak a public health emergency of continental security on Tuesday, its first such declaration since its formation in 2017.

More than 17,000 mpox cases and more than 500 deaths have been reported in 13 countries in Africa this year, according to the Africa CDC, which classifies the outbreak as a “very high risk event.” More than 14,000 of the cases where detected in the DRC.

WHO Regional Director for Africa, Dr Matshidiso Moeti said “significant efforts” are already underway in close collaboration with affected communities and governments to help reinforce measures to curb mpox.

“With the growing spread of the virus, we’re scaling up further through coordinated international action to support countries bring the outbreaks to an end,” she said.

Caused by an Orthopoxvirus, mpox was first detected in humans in 1970, in the DRC. The disease is considered endemic to countries in central and west Africa.

According to WHO, mpox has been reported in the DRC for more than a decade, and the number of cases reported each year has increased steadily over that period.

Last year, reported cases increased significantly, and already the number of cases reported so far this year has exceeded last year’s total, with more than 15 600 cases and 537 deaths.

Last week, the WHO Director-General triggered the process for Emergency Use Listing for mpox vaccines, which will accelerate vaccine access for lower-income countries which have not yet issued their own national regulatory approval. Emergency Use Listing also enables partners including Gavi and UNICEF to procure vaccines for distribution.

“WHO is working with countries and vaccine manufacturers on potential vaccine donations, and coordinating with partners through the interim Medical Countermeasures Network to facilitate equitable access to vaccines, therapeutics, diagnostics and other tools,” it said.

“WHO anticipates an immediate funding requirement of an initial $15mn to support surveillance, preparedness and response activities. A needs assessment is being undertaken across the three levels of the Organization.”

There are two types of mpox, clade I and clade II. Clade I usually causes a higher percentage of people with mpox to get severely sick or die compared to clade II. Clade I mpox occurs regularly, or is endemic, in the DRC.