The World Health Organization (WHO) has declared mpox a global health emergency for the second time in two years. While mpox didn’t disappear between the two outbreaks, the WHO’s latest announcement indicates it is once again a major health concern worldwide.
The current mpox outbreak is primarily concentrated in Africa, where the virus has been endemic in certain regions for some time. The illness is particularly widespread in the Democratic Republic of the Congo (DRC), but cases are also reported in countries such as Burundi, Nigeria, Kenya, Uganda, and the Central African Republic. The U.S. and the UK have each reported a travel-associated case related to this outbreak.
The WHO currently assesses the risk to individuals in other parts of the world as “moderate.” Here’s a summary of what to know about mpox in 2024.
How is this outbreak different from 2022?
Dr. Krutika Kuppalli, an infectious disease physician who participated in the WHO’s mpox response during the 2022 outbreak, explains that the current outbreak presents a more complex situation compared to what the world faced two years ago.
The 2022 outbreak was associated with a specific strain of the virus: clade 2b. While this clade didn’t entirely disappear, many countries successfully contained its spread. Now, cases linked to clade 2b continue to be identified in several locations, while countries in Central and Eastern Africa are also reporting cases related to another strain, known as clade 1. Some countries, including the DRC, have observed cases stemming from a newly identified subvariant of clade 1, labeled clade 1b. “We’re still learning about this new variant,” Kuppalli states.
Health authorities including the U.S. Centers for Disease Control and Prevention (CDC) indicate that clade 1b is potentially more severe than clade 2b, and have estimated the case fatality rate of the new clade 1b as high as 6%. However, findings released in August suggest that clade 1 has a lower mortality rate than initially believed—around 1.7%—when patients receive appropriate medical care. A study published in Nature Medicine in June also found that about 1.4% of patients infected with the new variant died. Kuppalli says emerging reports from the region suggest the rate may be even lower, around 0.7%, which is an encouraging development.
How is mpox spreading?
Individuals with mpox often experience flu-like symptoms before developing a blister-like rash. They are considered contagious until the rash has fully healed, according to the CDC.
Mpox is commonly transmitted through direct skin-to-skin contact with an infected individual. However, it can also spread through exposure to infected animals, contact with a sick person’s bodily fluids, or from a pregnant person to their fetus, as stated by the CDC.
During the 2022 outbreak, sexual contact among men who have sex with men was a significant contributing factor to transmission worldwide. Sexual contact still contributes to a high percentage of cases, . But during the current outbreak in Africa, the virus also appears to be spreading through non-sexual forms of person-to-person contact, the agency indicates. in the DRC—primarily with the original clade 1 strain, which is known to affect children, Kuppalli explains.
Reasons for shifting transmission patterns are “probably multifactorial,” she says. Possible reasons include decreased population-wide immunity since people are no longer routinely vaccinated against smallpox (which is similar to mpox), changes to the virus itself, increasing spillover from animals, or the prevalence of compounding health problems—like other infections or malnutrition—that make people more vulnerable. There also seems to be some animal-related transmission occurring in the DRC, according to .
Are mpox rates going up in the U.S.?
As of Aug. 22, the U.S. linked to clade 1 mpox. However, cases related to the strain responsible for the 2022 outbreak continue to be diagnosed. “People forgot mpox was still here,” says Dr. Jason Zucker, an infectious disease physician at NewYork-Presbyterian/Columbia University Irving Medical Center. “Even though mpox left the news and we thought about it a lot less, that doesn’t mean it actually went away.”
More than 1,700 mpox cases have been reported in the U.S. so far this year, according to preliminary CDC . That’s significantly lower than during the initial outbreak, when from 2022 into the first half of 2023.
Even with clade 2b continuing to spread, Zucker expresses optimism that cases will not reach levels comparable to the previous surge. Mpox’s spread in 2022 was unexpected, leaving laboratories, physicians, and public-health systems . Currently, Zucker says, individuals with symptoms are more efficiently diagnosed, tested, and treated, and vaccines are available for those who require them.
Should I get vaccinated?
The CDC’s Advisory Committee on Immunization Practices only for people with certain risk factors, such as men who have or expect to have multiple male sexual partners. With risk of transmission currently low for the general U.S. public, “there’s no reason right now for anyone who’s not in vulnerable populations to be running out to get a vaccine,” Zucker says.
Researchers are still investigating whether existing mpox vaccines are effective against the new clade. Real-world data is currently limited, but there is good reason to believe they will be effective, says Alessandro Sette, co-director of the Center for Vaccine Innovation at the La Jolla Institute for Immunology. The currently used shots are effective against both smallpox and mpox, suggesting they possess a fairly broad efficacy, Sette explains. Pox viruses also tend to mutate less dramatically compared to viruses like SARS-CoV-2 and influenza, he notes.
To help contain the outbreak, the U.S. has to the DRC, along with financial support for vaccine rollout. Countries such as and are also donating shots.
Kuppalli emphasizes the importance of scaling up surveillance, testing, and high-quality medical treatment in the affected region. “The focus really needs to be on where the outbreak is happening right now, which is in Africa,” she says. “In some cases, that [fact] has been lost a little bit.”
