California Urges Mpox Vaccination After More-Severe Strain Detected in San Francisco

State officials warn of new mpox variant with increased severity in the Bay Area.

Apr. 18, 2026 at 8:59pm by

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An extreme close-up X-ray image showing the intricate network of vessels and nodes within a human lymph node, glowing against a dark background to represent the internal workings of the body's immune system.A new, more severe strain of the mpox virus has been detected in San Francisco, prompting urgent calls for vaccination among high-risk residents.San Francisco Today

California health officials are urging high-risk residents to get vaccinated against mpox after a potentially more-severe strain of the virus was detected for the first time in San Francisco. The new variant appears to cause more severe symptoms compared to previous mpox outbreaks.

Why it matters

Mpox, formerly known as monkeypox, has been a growing public health concern in California and across the United States. The detection of a more virulent strain in San Francisco, a major urban center, raises alarm bells about the potential for wider spread and more serious illness, especially among vulnerable populations.

The details

State epidemiologists confirmed the presence of the new mpox variant after analyzing samples from recent cases in the San Francisco Bay Area. Compared to the original mpox strain, this variant appears to lead to more intense rashes, fever, and other symptoms. Health officials are urging anyone at high risk, including men who have sex with men, to get vaccinated as soon as possible to prevent further transmission and severe outcomes.

  • The new mpox variant was first detected in San Francisco in early April 2026.

The players

California Department of Public Health

The state agency responsible for monitoring and responding to public health emergencies in California.

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What they’re saying

“We are seeing a concerning uptick in mpox cases with this new strain, and vaccination is the best way to protect our communities from severe illness.”

— Dr. Tomás Aragón, Director, California Department of Public Health

What’s next

Health officials plan to increase mpox vaccine distribution and outreach efforts in the San Francisco Bay Area in the coming weeks to curb the spread of the new variant.

The takeaway

The detection of a more severe mpox strain in San Francisco underscores the need for continued vigilance and proactive vaccination, especially among high-risk populations, to stay ahead of evolving public health threats.