CDC investigating possible mpox resurgence amid dozens of new cases nationwide

The U.S. Centers for Disease Control and Prevention said Wednesday it was working with multiple health departments to investigate new mpox cases around the country, less than a month after officials had hailed the weekly pace of new infections slowing to zero nationwide.

News of the CDC’s investigations come a day after Chicago health officials warned they had tracked a resurgence of infections from mpox, formerly called monkeypox, many among fully vaccinated residents.

“Most weeks we didn’t see a single mpox case, maybe one or two in a higher week. But just these last couple of weeks we saw two, then five, now another six coming in,” Dr. Allison Arwady, commissioner of Chicago’s health department, said Tuesday.

Of 13 newly confirmed or probable cases in the city, nine of them were among men who had been fully vaccinated, local officials said in an alert distributed to healthcare providers. 

None of the 13 patients were hospitalized. Four disclosed recently traveling outside Chicago: to New York City, New Orleans and Mexico, the Chicago Department of Health reported. 

The CDC says it still recommends at-risk Americans get two doses of the Jynneos vaccine to guard against the virus, but urged doctors to test all patients with symptoms regardless of their vaccination status. 

“Getting vaccinated is still very important. No vaccine is 100% effective, and infections after vaccination are possible, but they may be milder and less likely to result in hospitalization,” the CDC said in a post published this week.

The number of new cases

After the CDC’s last tally on April 26, health officials had hailed the nationwide rolling average of new cases slowing to zero.

Since then, a total of 60 more cases have been reported to the CDC across eight states. 

Two states have added more than a dozen infections to their tallies: 31 in Texas and 15 in Illinois. A handful more cases have also been reported in California, Louisiana, New York, Alabama, Florida and Oregon. 

However, not all of these additional cases were actually diagnosed over the past two weeks. 

“At least 17 of the newly reported cases are from 2022 and three are from January and February of this year,” Lara Anton, a spokesperson for the Texas Department of State Health Services, said in an email. 

Anton said the department had recently worked with a local jurisdiction “to reconcile some of their cases.”

“The CDC also had an issue with processing our cases in their system recently so we believe that there may also be a few duplicate cases that were counted in the most recent data,” added Anton. 

A CDC spokesperson did not immediately respond to a request for comment.

Risk of resurgence

Health officials have been warning for months that they feared a potential resurgence of mpox, especially around travel and gatherings linked to Pride festivities over the coming months.

CDC modeling earlier this year had predicted an ongoing risk of resurgent outbreaks across many U.S. communities which could be further worsened by waning immunity.

“Monkeypox virus infection and vaccination are likely to confer some immune protection for years, based on evidence from smallpox disease and vaccination,” the agency’s modelers wrote. “However, if this protection wanes quickly or does not effectively stop transmission of the virus, resurgent outbreaks would be more likely.” 

Overseas, newly reported cases have climbed in Asia over recent weeks, according to World Health Organization figures, with dozens of new cases reported in Japan, China, and South Korea. New cases also continue to be reported in other parts of the world, including in the Americas.

“So while there is a downward trend globally, we know that the virus continues to transmit in certain communities and countries, such as in the Western Pacific region, and we continue to see travel-related cases,” Dr. Tedros Adhanom-Ghebreyesus, director-general of the World Health Organization (WHO), said Wednesday. 

Tedros was speaking at a WHO meeting in which the agency was weighing whether to end the mpox public health emergency. The U.S. public health emergency for mpox already ended in January.

“Unfortunately, many countries are now slowing down on surveillance and reducing access to tests and vaccines. It remains important for countries to maintain their capacities and continue their efforts,” he said.