The World Health Organization declared Wednesday that the increasing spread of mpox in Africa is a global health emergency, warning the virus might ultimately spill across international borders.

The announcement by WHO director-general Tedros Adhanom Ghebreyesus came after a meeting of the U.N. health agency’s emergency committee.

The Africa Centers for Disease Control and Prevention declared mpox a public health emergency on the continent on Tuesday.

WHO said there have been more than 14,000 cases and 524 deaths in Africa this year, which already exceed last year’s figures.

So far, more than 96 percent of all cases and deaths are in a single country — Congo. Scientists are concerned by the spread of a new version of the disease there that might be more easily transmitted among people, Associated Press reported.

Here’s a look at what we know about mpox, and what might be done to contain it:

What is mpox?

Mpox, also known as monkeypox, was first identified by scientists in 1958 when there were outbreaks of a “pox-like” disease in monkeys.

Until recently, most human cases were seen in people in central and West Africa who had close contact with infected animals.

Mpox belongs to the same family of viruses as smallpox but causes milder symptoms like fever, chills and body aches. People with more serious cases can develop lesions on the face, hands, chest and genitals.

What’s happening in Africa that’s causing all this concern?

The number of cases has jumped dramatically. Last week, the Africa CDC reported that mpox has now been detected in at least 13 African countries. Compared with the same period last year, the agency said cases are up 160 percent and deaths have increased by 19 percent.

Earlier this year, scientists reported the emergence of a new form of mpox in a Congolese mining town that can kill up to 10 percent of people and may spread more easily.

WHO said mpox was recently identified for the first time in four East African countries: Burundi, Kenya, Rwanda and Uganda. All of those outbreaks were linked to the epidemic in Congo. Tedros said there was concern for the further spread of the disease within Africa and beyond.

In the Ivory Coast and South Africa, health authorities have reported outbreaks of a different and less dangerous version of mpox that spread worldwide in 2022.

What does an emergency declaration mean?

WHO’s emergency declaration is meant to spur donor agencies and countries into action. But the global response to previous declarations has been mixed.

Africa CDC Director General Dr. Jean Kaseya said the agency’s declaration of a public health emergency was meant “to mobilize our institutions, our collective will and our resources to act swiftly and decisively.” He appealed to Africa’s international partners for help, saying that the escalating caseload in Africa had largely been ignored.

Greg Ramm, Save the Children’s Congo director, said the organization was particularly worried about the spread of mpox in the crowded camps for refugees in the east, noting there were 345,000 children “crammed into tents in unsanitary conditions.”

He said the country’s health system was already “collapsing” under the strain of malnutrition, measles and cholera.

WHO had already released $1.45 million from its emergency fund to support the response to mpox in Africa, but said it needs an initial $15 million to fund that response.