With Pride events scheduled around the world in the coming weeks, U.S. officials are preparing for the return of mpox, the infectious disease formerly called monkeypox that affected tens of thousands of gay and bisexual men around the world. in 2022. A combination of behavioral changes and vaccination quelled that outbreak. , but most people at risk have not yet been immunized.
On Thursday, the Centers for Disease Control and Prevention warned of a deadlier version of mpox ravaging the Democratic Republic of the Congo and urged people at risk to get vaccinated as soon as possible. To date, no cases of this subtype have been identified outside of Africa. But the growing epidemic in Congo nonetheless poses a global threat, just as infections in Nigeria triggered the 2022 outbreak, experts said.
“This is a very important example of how an infection anywhere is potentially an infection everywhere, and why we need to continue to improve disease surveillance globally,” said Anne Rimoin, an epidemiologist at the University of California, Los Angeles. Angels.
Dr. Rimoin has studied mpox in the Congo for more than 20 years and first warned of its potential for global spread in 2010.
The CDC is focusing on encouraging Americans most at risk to get vaccinated before the virus reappears. The agency’s outreach efforts include collaboration with advocacy groups and social media influencers who have broad appeal among the LGBTQ community. In December, the agency urged doctors to remain alert for possible cases in travelers from the Congo.
There are two main types of mpox: Clade I, the dominant type in the Congo, and Clade II, a version of which caused the 2022 global outbreak. (A clade is a genetically and clinically distinct group of viruses.) Both clades have circulated in Africa for decades, causing sporadic outbreaks.
People with mpox may have fever, severe headache, and back pain, followed by a rash. Many patients also develop painful sores, often at the site of the infection. People who have weakened immune systems, including those living with HIV, are more likely to become seriously ill and die.
The version of mpox that caused the 2022 outbreak, called Clade IIb, caused more than 30,000 cases in the United States that year. The epidemic subsided in 2023 with only about 1,700 cases, but is now showing signs of a resurgence: The number of cases in the United States this year is almost double what it was at this time last year.
In Congo, as of April 14, the Clade I virus has caused about 20,000 cases and almost 1,000 deaths since January 2023. Clade I infection has a mortality of about 5 percent, compared to less than 0 .2 percent for Clade IIb.
More than three-quarters of deaths in Congo related to Clade I mpox occurred among children under 15 years of age.
Even if the deadliest clade emerged in the United States, American children would be less likely to be exposed to mpox and less vulnerable to it than those in the Congo, experts said.
Most cases among children in the Congo are believed to be due to direct contact with infected animals, such as monkeys, prairie dogs, squirrels and shrews, or consumption of contaminated bushmeat. Children may live in overcrowded homes and have poor overall health.
The country suffers from armed conflict, floods, poverty, malnutrition and multiple infectious diseases, such as cholera, measles and polio.
“There’s just a difference in life in the DRC that likely promotes greater spread among children,” said Dr. Jennifer McQuiston, deputy director of the CDC’s Division of High Consequence Pathogens.
Adult cases in Congo have also been attributed to interactions with infected animals or close, sustained contact with infected people. But last year, for the first time, scientists discovered sexual transmission of Clade I mpox between male and female sex workers and their contacts.
In an outbreak in Kamituga, a mining town in the Congo, heterosexual prostitution in bars appeared to be the main form of transmission. Genetic analysis showed that around September the virus acquired mutations, allowing it to spread more easily between people.
This chain of transmission appears to be a second distinct outbreak in the country, caused by a new version of the virus called Clade Ib, with cases split almost equally between young men and women, said Marion Koopmans, a virologist at the Erasmus Medical Center in Rotterdam, Netherlands. Low.
“I think there is more than one outbreak going on and it’s important to continue to evaluate what that means,” Dr. Koopmans said. “We can’t assume” that all forms of mox behave the same way, he said.
The development has also alarmed scientists because the region’s miners and sex workers are transient and can carry the virus to the neighboring nations of Rwanda, Burundi, Uganda and Tanzania.
In many of these countries, limited access to tests, vaccines and treatments gives the virus ample opportunity to thrive and evolve. The vast majority of mpox cases are diagnosed based on symptoms alone.
Some countries rely on tests that detect only Clade I or only Clade IIb. Those tests may not detect Clade Ib, the new version that emerged in September, according to a recent study.
That finding prompted the World Health Organization to alert nations to review their testing procedures “and make sure they don’t miss a diagnosis,” said Dr. Rosamund Lewis, who leads WHO’s response to mox. .
In the United States, a test approved by the Food and Drug Administration detects all versions of mpox but cannot distinguish them. A positive result on that test should be followed by more specific tests that can identify the clade, Dr. McQuiston said.
At least so far, the available vaccines and antiviral drugs are expected to be effective against all forms of the virus. The 2022 outbreak began in Europe in May and gained strength in the United States during Pride Month in June and later.
Early in the outbreak, there was a shortage of the two-dose mpox vaccine, called Jynneos. But many gay and bisexual men, accustomed to paying attention to public health messages about HIV, curbed their sexual activity, precipitating a decline in cases even before vaccines became widely available.
However, the drop in numbers may have produced a false sense of security.
“There was a sense of complacency because this wasn’t really something that people had to constantly worry about, and we saw those vaccination rates decline rapidly,” said Dr. Boghuma Titanji, a virologist and infectious disease physician at the Emory University.
Behavioral changes are difficult to maintain, so vaccination is important for long-term virus control, Dr. Titanji said.
Two doses of the vaccine are more potent than one, with up to 90 percent efficacy, according to an analysis last month of 16 studies. Even when the vaccine did not prevent infections, it moderated the severity and duration of the disease.
Still, fewer than one in four at-risk Americans have received two doses.
“We’ve continued to saturate the space with messages, and acceptance isn’t really changing much,” Dr. McQuiston said, suggesting the need for more creative approaches.
In 2022, the vaccine was available only in the United States through federal agencies and was plagued by delivery problems, limiting its availability; It is now commercially available. The WHO, which recommends vaccines for African countries, has been slow to approve them and has not even started the approval process.
Still, the WHO’s advisory group on immunizations has recommended that, when available, the vaccine can be used to protect adults and children at risk of contracting mox, Dr. Lewis said.
In addition to preparing for mpox’s return to the United States, CDC is supporting Congo’s efforts to obtain vaccines and medicines and contain the epidemic.
“It is much better to help them control this outbreak before it spreads to other areas and becomes a global risk,” Dr. McQuiston said. “And, ethically, it’s the right thing to do.”