Mpox: Acting globally, preparing locally

CDC works with the DRC Ministry of Health to help control infectious diseases such as mpox and Ebola. In this photo, a Ministry of Health surveillance team and community healthcare workers monitor contacts of people diagnosed with Ebola during a 2018-2020 outbreak. Photo by Mary Claire Worrell/CDC

Mpox has become all too familiar around the world in the past two years. But in central Africa, it’s been a recurring health threat for decades.

An ongoing outbreak of mpox in the Democratic Republic of the Congo (DRC) has become larger and more widespread than any previous outbreak there, with more than 18,000 suspected and confirmed cases since January 2023. The type, or clade, of the virus behind this mpox outbreak is also more likely to cause severe illness or death than the type that caused the global mpox outbreak that began in 2022.

CDC has been studying mpox in the DRC for more than 20 years and has helped its authorities respond to other infectious diseases, including HIV, TB, and Ebola. For the current mpox outbreak, CDC has funded contact tracing and community outreach work. CDC worked with DRC national public health agencies to evaluate mpox testing at DRC laboratories in two provinces where the virus commonly circulates, because having more labs available to test for mpox would allow a faster response to cases. And CDC experts will continue to work with DRC’s Ministry of Health to analyze data from case reports and lab tests.

“We’re working with DRC and looking for any indication that this could become a bigger problem there or other places around the globe,” says CDC disease ecologist Yoshinori Nakazawa, who has studied the disease for much of his career.

Mpox has been present in DRC since the first human cases were discovered there in 1970. The virus that causes it often spreads from animals to people, either through animal bites or touching contaminated animal carcasses. People who are infected with mpox may then spread it to other household members through close contact.

During the current DRC outbreak, many possible cases have been in children, suggesting traditional means of spread from animals to people and then between people through close contact. But in a few locations, the DRC outbreak is being spread by sexual contact, including female sex workers – the first time that’s been documented for this type of mpox in DRC.

“Right now, we’re trying to better understand how mpox is spreading in the outbreaks occurring in DRC, because each outbreak can be different,” says Victoria Shelus, an officer in CDC’s Epidemic Intelligence Service. “As we better understand the data, we are able to make recommendations for next steps.”

CDC’s assistance to DRC is part of a broader U.S. government effort to help control this outbreak and prepare domestically. Nine departments and agencies, including the U.S. State Department; U.S. Agency for International Development; and the Administration for Strategic Preparedness and Response in the Department of Health and Human Services, are part of an integrated U.S. government mpox response team.

At this time, no cases of mpox caused by the DRC outbreak have been seen outside that country or in the United States. But the ongoing 2022 global mpox outbreak showed the disease was capable of spreading rapidly beyond its normal range.

The lessons of 2022

Before the 2022 global outbreak, the few mpox cases outside Africa occurred in travelers who had visited countries where mpox is naturally present in the environment, and one outbreak in the U.S. Midwest that involved a shipment of wild mammals from Ghana. Transmission to others in close contact was rare. The 2022 outbreak involved a type of mpox that is less severe than the one circulating in DRC – but it was also the first time that most cases were spread through sexual contact. It spread rapidly through intimate, person-to-person contact, largely among gay, bisexual, and other men who have sex with men.

The 2022 outbreak has caused more than 92,000 illnesses around the world, including more than 32,000 cases and 56 deaths in the United States. The U.S. outbreak was brought under control by a combination of community outreach efforts with LGBTQ+ organizations—which emphasized how people most at risk could protect themselves— and the first wide distribution and use of the two-dose JYNNEOS vaccine.

“The steps we took during the mpox outbreak that started in 2022 will help us quickly detect and respond to any new mpox cases in the United States, even this more severe form of the virus,” says Jennifer McQuiston, principal deputy director of CDC’s Division of High Consequence Pathogens and Pathology. “Before 2022, most U.S. healthcare providers had never seen mpox cases before. But now they’re more confident in quickly recognizing and safely managing patients, and mpox testing for patients is widely available in laboratories across the country.”

JYNNEOS was developed as part of U.S. defenses against a possible smallpox bioterror attack. But data from the 2022 outbreak shows JYNNEOS proved effective against mpox as well, and the United States has ample supplies stockpiled and ready to use, McQuiston says. The two-dose vaccine is now recommended for people 18 and older who are at risk of mpox during mpox outbreaks.

And although no cases of mpox of the type being seen in the DRC have been identified in countries outside central Africa, CDC has warned U.S. healthcare providers and health departments to keep an eye out for people who have rashes or sores that might be a symptom of mpox, especially if they have been in or had contact with others who have been in the DRC recently.

CDC is still tracking the virus involved in the 2022 outbreak closely, including looking for signs of the virus that causes the disease in wastewater collected from planes at select airports and U.S. communities. Those programs have also begun to keep watch for the type of virus behind the DRC outbreak. The work that Nakazawa, Shelus, and other CDC experts are doing is aimed at containing the outbreak in DRC while preparing to respond if cases appear in the United States.

“As COVID-19 and as the mpox outbreak that started in 2022 have shown us, people are moving around the world, and it can be hard to contain diseases,” Shelus says. “A threat anywhere is a threat  everywhere.”