WHO may declare new, deadlier mpox outbreak an international emergency

Editor's note: Following publication of this story, the World Health Organization declared the outbreak a public health emergency of international concern on Aug. 14.

A growing outbreak of mpox in Africa may soon prompt the World Health Organization (WHO) to declare a public health emergency of international concern.

So far, the multinational outbreak has been concentrated mostly in the Democratic Republic of the Congo (DRC), which has reported more than 14,000 cases of mpox this year, WHO Director-General Tedros Adhanom Ghebreyesus said at a news conference Wednesday (Aug. 7).

The outbreak in the DRC has been underway since 2023, when the country reported about 12,600 suspected cases and 580 deaths from mpox between January and early December. That represented a major increase over previous years, when a median of only 3,770 suspected cases had been reported annually, according to the Centers for Disease Control and Prevention (CDC).

Now, "the number of cases reported in the first six months of this year [2024] match the number reported in all of last year and the virus has spread to previously unaffected provinces," Tedros said at the news conference. In addition, in the past month, 50 cases have been confirmed and more are suspected in Burundi, Kenya, Rwanda and Uganda, which neighbor the DRC, he said.

Related: 'Mpox' is the new name for monkeypox, the WHO says

"In light of the spread of Mpox outside DRC, and the potential for further international spread within and outside Africa, I have decided to convene an Emergency Committee under the International Health Regulations to advise me on whether the outbreak represents a public health emergency of international concern," Tedros said. That committee will meet "as soon as possible," he added.

Mpox viruses are divided into multiple "clades" that differ in their deadliness. The clade that fueled the global mpox outbreak in 2022 and 2023, known as clade 2, had a case-fatality rate of around 0.2% during that outbreak.

By comparison, the case-fatality rate for clade 1 mpox viruses runs up to 10%. Clade 1 viruses have never been detected in the U.S. or anywhere beyond countries where mpox regularly spreads, such as the DRC, but international travel could introduce the germs to new places.

The ongoing outbreak in Africa features a new branch of the clade 1 family tree, dubbed clade 1b. Genetic analyses suggest that this new branch emerged in September 2023 in the DRC. The virus has been spreading through households and within sexual networks, and its fatality rate has been estimated between 3% and 6%, according to CIDRAP News, which is published by the University of Minnesota.

"Clade 1b has been confirmed in Kenya, Rwanda and Uganda, while the clade in Burundi is still being analyzed," Tedros said.

Experts anticipated that clade 1b would spill beyond the DRC's borders. "People are very mobile at the eastern part of the country with great connection with neighboring countries," Dr. Placide Mbala, an epidemiologist at the DRC's National Institute of Biomedical Research, told Science. "It was just a matter of time to start seeing cases in those neighbor countries."

The WHO has released funding to ramp up mpox response in affected countries and is working to improve access to the two available mpox vaccines. In addition, Science reported that a clinical trial preparing to launch in Africa will test the vaccines as a treatment to use after an mpox exposure.

The CDC issued a health alert about the outbreak on Aug. 7, highlighting that, since January 2023, "the DRC has reported the largest number of yearly suspected clade I mpox cases on record." The agency recommends that U.S. clinicians look out for mpox in patients who are displaying potential symptoms and have recently been to the DRC or any of its neighboring countries. That said, the risk of clade 1 mpox viruses being imported to the U.S. is currently considered "very low."

"No cases of clade I mpox have been reported outside central and eastern Africa at this time," the health alert states.

Meanwhile, in the U.S., hundreds of cases of clade 2 mpox had been reported earlier in the year, between January and April. A trickle of new cases is still being reported now, but the latest CDC data suggest the rate has been tapering off throughout the summer.

Editor's note: This story was updated at 5:00 p.m. on Aug. 7, 2024, to note that the CDC had released a health alert about the outbreak. The story was initially posted at 3:00 p.m. the same day.

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