GENEVA, Switzerland (AFP)— The World Health Organization (WHO) said Friday it had decided to keep its alert for the mpox epidemic at the highest level, as the number of cases and countries affected rises.

“The decision was based on the rising number and continuing geographic spread of cases, operational challenges in the field, and the need to mount and sustain a cohesive response across countries and partners,” it said in a statement.

“The WHO Director-General, agreeing with the advice of the (International Health Regulations) IHR Emergency Committee, has determined that the upsurge of mpox continues to constitute a public health emergency of international concern,” it said, extending the emergency first declared on August 14.

The Democratic Republic of Congo (DRC) is the country hardest hit by the outbreak, followed by Burundi and Nigeria.

Mpox, previously known as monkeypox, is caused by a virus transmitted to humans by infected animals but can also be passed from human to human through close physical contact.

It causes fever, muscular aches and large boil-like skin lesions, and can be deadly.

The August emergency declaration was in response to a surge in cases of the new Clade 1b strain in the DRC that spread to nearby countries.

That and other mpox strains have been reported across 80 countries — 19 of them in Africa — so far this year, WHO has previously said.