San Francisco Confirms First Case of Clade I Mpox

On April 14, 2026, the San Francisco Department of Public Health confirmed the city’s first case of clade I mpox in an unvaccinated adult who had close contact with someone who traveled internationally. The individual was hospitalized and is improving.

What is Clade I Mpox?

Clade I mpox is a variant of the virus formerly known as monkeypox. It has been circulating in eastern and central Africa since 2023, causing more than 53,000 cases and at least 200 deaths among children and adults in that region. Health officials note that this strain may cause more severe illness than the clade II variant responsible for the 2022 global outbreak.

Case Details and Public Health Response

The infected individual reported close contact with a person who had traveled internationally. San Francisco health officials emphasize that the risk to the general public remains low, but they urge individuals at higher risk of exposure to secure fully vaccinated with the two-dose mpox vaccine. Dr. Susan Philip, San Francisco’s health officer, stated that although clade I mpox cases remain rare in the United States, clade II cases continue to occur in the city and throughout California, underscoring the importance of vaccination for those at risk.

Vaccination and Prevention

Health officials encourage anyone at risk of contracting mpox to get vaccinated, as the vaccine is effective against both clade I and clade II strains. The vaccine is available through healthcare providers and public health clinics in San Francisco. Individuals should consult their doctor or local health department for information on vaccine access and eligibility.

National Context

As of March 2026, the Centers for Disease Control and Prevention had reported 15 clade I mpox cases in the United States since late 2024, with over a quarter of these cases diagnosed in March 2026 alone. All U.S. Cases of clade I mpox are not linked and occurred in individuals with recent travel to areas associated with the outbreak in Central and Eastern Africa or parts of Western Europe with more recent outbreaks, or through close contact with such travelers.

Key Takeaways

• San Francisco has confirmed its first case of clade I mpox, a variant that may cause more severe illness.
• The case involved an unvaccinated adult with close contact to an international traveler.
• The risk to the general public remains low, but vaccination is recommended for those at higher risk.
• The mpox vaccine is effective against both clade I and clade II strains.
• Health officials continue to monitor the situation and emphasize prevention through vaccination.

Frequently Asked Questions

What is the difference between clade I and clade II mpox?

Clade I mpox has been circulating in eastern and central Africa since 2023 and is associated with more severe illness and higher mortality, particularly among children. Clade II mpox was responsible for the 2022 global outbreak and generally causes less severe disease.

How does mpox spread?

Mpox spreads through close skin-to-skin contact, including sexual contact, and through contact with contaminated materials such as bedding or clothing. It can also spread via respiratory droplets during prolonged face-to-face contact.

Who should get the mpox vaccine?

Individuals at higher risk of exposure, including those with multiple sexual partners, healthcare workers, and people who have had close contact with someone infected with mpox, should consider vaccination. Consult a healthcare provider for personalized advice.

Is the mpox vaccine safe and effective?

Yes, the mpox vaccine is safe and effective. It is a two-dose vaccine that provides protection against both clade I and clade II strains of the virus.

Where can I get the mpox vaccine in San Francisco?

The mpox vaccine is available through healthcare providers, public health clinics, and community health centers in San Francisco. For specific locations and eligibility, contact the San Francisco Department of Public Health or visit their website.

As summer travel and events approach, health officials remind the public to stay informed about mpox risks and prevention strategies. Vaccination remains the most effective way to protect against both known strains of the virus.