What to Know About Mpox

Mpox was declared a global health emergency on Wednesday for the second time in three years, as the World Health Organization urged action on a virus spreading rapidly through more than a dozen African countries.

The outbreak is most severe in the Democratic Republic of Congo, which has reported 15,600 mpox cases and 537 deaths, according to the U.N. agency. The mpox epidemic there has already proved more deadly than one in 2022, the last time an emergency was announced.

Here is what to know about mpox, which was known as monkeypox before health officials, responding to complaints about the word, recommended its current name in 2022.

What is mpox and how is it spread?

The mpox virus is endemic to Central and Western Africa. The disease is similar to smallpox but less contagious, and the virus is spread primarily through close contact with infected animals or people, and the consumption of contaminated meat.

Mpox can also be spread through sexual contact, and there is a risk of transmission to a fetus.

Who is currently being affected?

Ninety-six percent of the mpox deaths reported in June were in Congo, a country already assailed by an internal conflict and humanitarian crisis. But the disease has now been identified in 13 countries, including for the first time in the East African nations of Burundi, Kenya, Rwanda and Uganda.

There are differences between the outbreaks in various regions and countries, depending on the circumstances in each community, according to Dr. Sylvie Jonckheere, an adviser on emerging infectious diseases for Doctors Without Borders. But they share a common feature, she said: “We do not know how to control this outbreak.”

Facing the threat of global spread, the Centers for Disease Control and Prevention in the United States has warned medical professionals and people in the country to remain on high alert.

What are the symptoms?

Fever, headache, muscle aches and a blistering rash that progresses to pustules and eventually scabs over can be signs of the disease. Symptoms can last two to four weeks, and treatment in many cases relies heavily on supportive care and alleviating symptoms.

Historically, the disease is more lethal to young children, people who are immunocompromised and those with comorbidities, such as H.I.V.

How is it being treated?

Though vaccines were used in 2022 during that epidemic, they are insufficient to curb the current crisis, experts say. “There are not enough vaccines in the world to do that,” said Dr. Jonckheere, who has recently assisted health care workers in Congo and Burundi.

Though not a comprehensive solution to slowing the disease, social distancing can help reduce its spread, Dr. Jonckheere said.

In 2022 in the United States, for example, as people received vaccinations and changed their behavior, the toll dropped to about 1,700 cases last year from more than 30,000 in 2022.

But in some places in Congo, such as camps for internally displaced people near the city of Goma in the North Kivu Province, the crowded conditions make isolation impossible. Congo has approved two mpox vaccines but has yet to carry out an immunization plan.

What is the history of the disease?

The disease was discovered in 1958, after outbreaks occurred in monkeys used for research. The first infection in a human was confirmed in 1970 in Congo.

The W.H.O. declared the mpox epidemic a global health emergency in July 2022, and the disease was detected in over 70 countries that had never previously reported mpox. Since then, it has affected nearly 100,000 people in 116 countries.

Though the outbreak has largely subsided in Europe, Asia and the Americas, it has worsened in parts of Africa. The Africa Centers for Disease Control and Prevention reported a 160 percent increase in the number of cases reported from the start of 2024 to July 28 compared with the same period last year.

Who is most at risk?

The strain of mpox that has been spreading in Congo has a death rate of 3 percent, much higher than the 0.2 percent death rate observed in the 2022 outbreak.

Women and children are most affected, according to Save the Children, an international charity, which said newborns as young as 2 weeks old are contracting the disease because of overcrowded hospitals.

In the affected areas, health care workers are treating patients of all ages, including families.

“It’s really heartbreaking when you see entire families end up in your treatment center,” Dr. Jonckheere said. “It’s the mom, it’s all the kids, including the very, very young ones.”