A new version of mpox that is spreading rapidly in the Democratic Republic of Congo and starting to show up in neighboring countries has yet to make its way to the United States, but public health experts are warning that New York City should be prepared in case the more deadly strain of the virus makes its way here.
The latest mpox strain was recently reported in Sweden, marking the first known case outside of Africa.
“The world has become a much smaller place and with any sort of infectious disease outbreak anywhere in the world, there’s always a concern that it could travel to new places,” said Dr. Richard Silvera, associate program director of the Infectious Diseases Fellowship at Mount Sinai Health System and assistant professor of infectious diseases at Mount Sinai’s Icahn School of Medicine.
New York City became the United States epicenter of a previous mpox outbreak in 2022 caused by a less severe version of the virus. There was an uptick in mpox cases this year compared with last year, but case counts have since leveled off and remain low at one or two cases per day, according to health department data.
Preparedness for a potential surge of the new mpox strain includes promoting vaccination and awareness of the signs and symptoms of mpox, while closely monitoring the disease, public health experts said.
New York City started tracking mpox cases in 2022, pushing public health measures and clinician guidance around the virus, according to Patrick Gallahue, a spokesperson for the city health department.
“We have learned many lessons from the 2022 outbreak and we are prepared,” Dr. Ashwin Vasan, the city health commissioner, said in a statement last week after the World Health Organization declared the current mpox outbreak in Africa a “public health emergency of international concern.”
But Vasan also noted that outbreaks can be unpredictable and emphasized the importance of remaining vigilant.
Here’s what New Yorkers should know about the new strain of mpox that’s circulating and the measures available to protect against and treat the virus.
What does mpox look like and how is this version of mpox different?
Mpox typically causes a rash that looks like pimples or blisters and comes with flu-like symptoms like a fever and chills, according to the U.S. Centers for Disease Control and Prevention.
The version of mpox currently circulating in the Democratic Republic of Congo, known as Clade I, is endemic to Central Africa and has a higher mortality rate than Clade II, the strain that was responsible for the 2022 outbreak that hit New York City.
More than 99.9% of people survive Clade II, while Clade I outbreaks have killed up to 10% of those infected, according to the CDC.
But that won’t necessarily be the case if the virus makes its way to the U.S., said Dr. Wafaa El-Sadr, an epidemiologist with the Columbia Mailman School of Public Health.
“Death and mortality depends very much on access to adequate health care,” she said. “This current outbreak of Clade I has occurred in countries that have rather fragile health systems overall.”
Is vaccination effective against the new strain?
The vaccine that’s been approved for mpox in the U.S. is up to 75% effective at preventing transmission after one dose and up to 85% after two doses, according to JYNNEOS, the vaccine manufacturer.
Those who have received doses of the vaccine for Clade II are also expected to be protected against the current strain circulating abroad, according to the U.S. Department of Health and Human Services.
Silvera said no boosters are recommended at the moment, but anyone who has only gotten one dose of the mpox vaccine should get the second one.
The city health department continues to recommend vaccination for those who have been at higher risk in the U.S. outbreak — specifically, people who have sex with men and also identify as male, trans or gender non-conforming. The vaccine is also recommended for anyone who’s recently been in close contact with someone they think has mpox.
How is mpox being monitored?
In a recent notice to health care providers, the city health department advised clinicians to ask patients with symptoms of mpox about their recent travel and the travel of anyone they’ve been in close contact with who also has mpox symptoms.
The health department noted that clinicians should then test for mpox and send specimens to a state public health laboratory or the CDC to determine the viral strain or clade.
Are there any treatments available?
The city health department is urging health care providers to sign patients with mpox up for a clinical trial of Tecovirimat, which currently has FDA approval for the treatment of smallpox.
Silvera of Mount Sinai said the treatment is typically recommended to people who are at high risk for severe symptoms, including those who are immunocompromised or have pre-existing skin conditions. But he said anyone with mpox should talk to their doctor about the treatment.
“It’s never a waste of time to inform a patient about what’s going on,” he said. “We’re happy to talk to everyone about it.”
What is the global response?
There is a growing push to send mpox vaccines and other resources to the areas most affected by the current outbreak.
“We must also advocate for resources to flow to the parts of the world most affected because we know stopping outbreaks at their source is the smartest way to respond,” Vasan said last week.
While the JYNNEOS vaccine quickly became available in New York City during the 2022 outbreak — albeit with some supply issues early on — there are still few doses available in Africa. The Democratic Republic of Congo is set to receive its first shipment of mpox vaccines from the United States next week.