LONDON (AP) — The Africa Centers for Disease Control and Prevention declared this week that the increasing spread of mpox across the continent is a health emergency, warning the virus might ultimately spill across international borders. On Wednesday, the World Health Organization is convening its own expert meeting to consider making a similar emergency declaration over mpox. So far, more than 96% 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. Here’s a look at what we know about mpox, and what might be done to contain it: 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.

In 2022, the virus was confirmed to spread via sex for the first time and triggered outbreaks in more than 70 countries that had not previously reported mpox. Most of those infected were gay and bisexual men. 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. 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.