Mpox strain surfaces in US without international travel, raising fears of wider outbreak

Oct 23, 2025 | Lifestyle, U.S., World

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A new strain of mpox, caused by the monkeypox virus, has surfaced in Southern California.

There have been three confirmed cases of clade I mpox, according to the California Department of Health (CDPH), which released a statement on Oct. 17.

The unrelated cases were identified in the City of Long Beach and Los Angeles County.

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The department warned that although public health risk remains low, this was the first time the patients did not have a history of recent international travel.

This indicates a person-to-person community spread, which can occur through intimate contact. Typically, mpox cases are brought in from outside the country.

monkeypox virus test in medic's hand

All three of the patients required hospitalization but are now in recovery.

CDPH urged residents at risk of contracting the disease from a partner to receive both doses of the mpox vaccine. Mpox often impacts communities of gay and bisexual men. 

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Both clade I and clade II mpox can spread through intimate physical contact; direct skin-to-skin contact with an mpox rash, scabs or body fluids; sharing a living space or personal items with an infected person; or from a pregnant woman to a fetus or baby, according to health agencies.

Casual contact, such as on an airplane, office or store, is unlikely to spread mpox, according to CDPH.

pharmacist's hand with latex glove holding photo of monkeypox virus

Assistant State Public Health Officer Dr. Rita Nguyen wrote in the CDPH notice that the department will continue to monitor the situation to reduce spread, recommending that Californians “stay informed and take preventive measures.”

“Especially [for] persons who are more likely to be exposed to mpox, clade I mpox cases can be severe,” she said. 

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“Risk of severe disease and hospitalization are highest for people with weakened immune systems, so it’s critical to protect yourself by getting both doses of the mpox vaccine if you or your sex partner(s) may be at risk for mpox.”

Mpox symptoms may first mimic the flu, followed by a rash. The virus can be diagnosed through lab testing.

Those exposed to mpox should get vaccinated as soon as possible and before symptoms develop, and should also avoid intimate contact for 21 days, according to health agencies.

Person receiving hospital care

People who develop symptoms should speak with their doctor immediately to undergo testing. Mpox-positive patients should isolate at home and avoid contact with others until the rash is healed.

In an interview with Fox News Digital, Dr. Thomas Ksiazek, professor of microbiology and immunology at University of Texas Medical Branch in Galveston, Texas, said the public “should be concerned” about this outbreak, although it’s not time for panic.

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“What’s really required is vigilance or surveillance … to detect new cases and try and stop them from being spread further,” he said. “There is a vaccine available that’s quite effective that should be used in the communities in which spread occurs.”

The zoonotic infection that is endemic in areas of Africa has become a sexually transmitted disease “somewhat recently,” Ksiazek noted.

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This in-state spread most likely began with someone who had a mild case and failed to report it after international travel, which the expert said highlights the need for surveillance.

“Finding cases early and making sure efforts are taken to stop spread is an important aspect of this,” he added.

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