California Confirms First U.S. Case of Severe Mpox Strain Without Travel History

October 16, 2025

California health officials have confirmed the first U.S. case of a more severe strain of mpox in a patient with no recent travel history. The case was identified in a Long Beach resident, who required hospitalization and is now recovering at home in isolation.

“We are taking this very seriously and ensuring our community and health care partners remain vigilant so we can prevent any more cases,” said Long Beach Mayor Rex Richardson. “This underscores the importance of continued surveillance, early response, and vaccination.”

About the Severe Mpox Strain

This is the seventh confirmed case of the more severe mpox strain in the U.S. this year, but it is the first without known travel to Africa, where the strain (Clade I) is endemic. Previously, all severe cases in the U.S. were linked to travel from African countries.

• Clade I: Historically associated with severe illness and death; endemic in central and western Africa.
• Clade II: Caused the 2022 global outbreak with over 100,000 cases worldwide, including 30,000+ in the U.S.

Public Health Response

Health officials emphasize that the risk to the general public remains low. The Long Beach Health Department is conducting a full investigation to identify potential sources of exposure for the patient.

Key measures being highlighted include:

• Vigilant community and healthcare surveillance
• Early detection and response to new cases
• Vaccination efforts in at-risk populations

What You Need to Know About Mpox

Mpox is caused by a virus related to smallpox. While Clade II has been circulating at low levels in the U.S., Clade I is considered more severe and can cause serious illness.

Health authorities urge people to stay informed, practice good hygiene, and seek medical care if they experience symptoms such as fever, rash, or swollen lymph nodes.

Conclusion

The identification of a severe mpox case with no travel history in California is a rare but serious development, highlighting the importance of continued monitoring, early detection, and vaccination to prevent wider spread.