New Monkeypox Strain Detected in San Francisco

Health officials urge vaccinations after case of rare clade I variant reported

Apr. 17, 2026 at 4:03am by

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An extreme macro X-ray photograph showing the ghostly, translucent structure of a human lymph node, hinting at the internal biological mechanisms affected by the monkeypox virus.A rare monkeypox variant detected in San Francisco raises concerns about the need for continued vaccination efforts to protect vulnerable populations.San Francisco Today

San Francisco's Department of Public Health has confirmed a case of the rare clade I strain of monkeypox in a city resident. The individual was not vaccinated but is improving after being hospitalized. Health officials are now encouraging high-risk groups, including gay and bisexual men, to get vaccinated, especially those planning to travel internationally.

Why it matters

The emergence of the clade I monkeypox strain in San Francisco is concerning, as it is less common in the United States compared to the clade II strain that caused an outbreak in the city in 2022. Public health experts are monitoring whether the clade I variant may be more severe, underscoring the importance of vaccination efforts to protect vulnerable communities.

The details

The infected individual came into contact with someone who had traveled internationally and carried the clade I monkeypox virus. Symptoms include fever, swollen lymph nodes, fatigue, and a characteristic rash. While the vaccine is safe even for immunocompromised individuals, it is not recommended for those previously infected with monkeypox.

  • On Tuesday, the SFDPH confirmed the first case of clade I monkeypox in a resident.
  • The infected individual was hospitalized but is now improving.

The players

San Francisco Department of Public Health

The local public health agency that reported the new case of the rare clade I monkeypox strain and is urging vaccination efforts.

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What’s next

Public health officials are monitoring the situation closely to determine if the clade I strain is more severe than the clade II variant. The city is encouraging high-risk groups to get vaccinated, especially those planning international travel.

The takeaway

The detection of the rare clade I monkeypox strain in San Francisco underscores the need for continued vaccination efforts to protect vulnerable communities, especially as new variants emerge. This case highlights the importance of public health vigilance and preparedness in responding to evolving infectious disease threats.