Clade I Mpox Outbreak Originating in Central Africa

Since January 2023, the Democratic Republic of the Congo (DRC) has reported more than 27,000 suspect mpox cases and more than 1,300 deaths.

There are two types of mpox, clade I and clade II. Clade I usually causes a higher percentage of people with mpox to get severely sick or die compared to clade II.

Clade I mpox occurs regularly, or is endemic, in DRC. The current outbreak is more widespread than any previous DRC outbreak, and clade I mpox has spread to some neighboring countries, including Burundi, Central African Republic, Republic of the Congo, Rwanda, Uganda, and a travel-associated case in Kenya. These countries are all reporting cases of clade I mpox, and some of them have links to DRC.

On August 14, 2024, the World Health Organization (WHO) declared the outbreak a Public Health Emergency of International Concern (PHEIC). This is the WHO’s highest level of global alert, and the decision recognizes the potential threat this virus poses to countries around the world. The declaration focuses international attention on acute public health risks that require coordinated mobilization of extraordinary resources by the international community for prevention and response. Read more about the United States Government’s response to the outbreaks in several African countries.

Situation in the United States

No cases of clade I mpox have been reported in the United States at this time.

CDC assessed the risk to the United States posed by the clade I mpox outbreak in the Democratic Republic of Congo and neighboring countries. The risk to the general population is assessed as low. The current risk to U.S. men who have sex with men with more than one sexual partner, and their partners, is assessed as low to moderate. The risk might change as more information becomes available.

Mpox needs close or intimate contact to spread, so casual contact like you might have during travel is not likely to cause the disease to spread. The best protection against mpox is two doses of the JYNNEOS vaccine if you’re eligible, People can also protect themselves by:

• Avoiding close contact with people who are sick with signs and symptoms of mpox, including those with skin lesions or genital lesions.
• Avoiding contact with wild animals (alive or dead) in areas where mpox regularly occurs.
• Avoiding contact with contaminated materials used by people who are sick (such as clothing, bedding, or materials used in healthcare settings) or that came into contact with wild animals.
• Avoiding eating or preparing meat from wild animals (bushmeat) or using products (creams, lotions, powders) derived from wild animals.

Situation in DRC

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There are several outbreaks happening at the same time in DRC, with cases reported throughout the country, in the capital city of Kinshasa, and in some other large cities. In DRC, different provinces have outbreaks with different features. In some provinces, patients have acquired infection through contact with infected dead or live wild animals, household transmission, or patient care (transmitted when appropriate PPE wasn’t used or available); a high proportion of cases have been reported in children younger than 15 years of age. In other provinces, the cases are associated with sexual contact among men who have sex with men and female sex workers and their contacts. These are first reported cases of sexual transmission with clade I mpox.

CDC has been supporting DRC mpox research and response for more than 20 years.  CDC and other U.S. government agencies are on the ground in DRC helping partners in the country with disease surveillance, laboratory capacity including testing materials, strengthening workforce capacity, case investigation, case management, infection prevention and control, border health, and risk communication and community engagement. DRC has approved the use of vaccines in-country, so CDC is working with other U.S. government agencies and partners on a strategy for vaccination in DRC.

Situation in Central and Eastern Africa

The Republic of the Congo (ROC), which borders DRC to the west, declared a clade I mpox outbreak in April 2024. There have also been confirmed clade I cases in Central African Republic (CAR), which borders DRC to the north. Clade I mpox is endemic to ROC and CAR, but the new cases appear to be linked to spread from DRC. In late July 2024, Burundi, Rwanda, and Uganda, which sit on the eastern border of DRC, reported confirmed cases of clade I mpox. Kenya has also reported two cases of travel-associated mpox. Clade I mpox has not been known to be endemic in these countries. Although contact tracing is ongoing, some cases have links to DRC. Person-to-person transmission has occurred during this outbreak, including through sexual contact, household contact, and within the healthcare setting.

CDC is working with Ministries of Health and in-country partners across the region on disease surveillance, laboratory capacity including testing materials, strengthening workforce capacity, case investigation, case management, infection prevention and control, border health, and risk communication and community engagement.

Global situation

• A case of clade I mpox in a Swedish traveler who visited an affected country in Africa was announced August 15. This is the first clade I mpox case to be reported outside of the African continent.
• Thailand announced August 22 that a traveler to that country from DRC was diagnosed with clade I mpox.

Given the widespread clade I outbreak in Central and Eastern Africa, a case diagnosed in an occasional traveler is not unexpected. Rapid detection and stopping any potential spread of mpox are key to stopping an outbreak.