Health officials in San Francisco say the city now has its first case of a newer, potentially more severe mpox strain.
This variant of mpox — the disease formerly called monkeypox — is known as clade I, and has been circulating in eastern and central Africa since 2023, where it’s caused more than 53,000 cases among children and adults and at least 200 deaths.
The disease usually spreads through close skin-to-skin contact, including sex.
On Thursday, the San Francisco Department of Public Health announced that the city’s first clade I mpox case had been confirmed in a resident earlier this week.
The patient, who had not received the mpox vaccine, was hospitalized and is improving, according to SFPDH.
The agency said that this clade I mpox patient had reported close contact with another person who had traveled internationally.
The Centers for Disease Control and Prevention said that until now, 15 cases of clade I mpox have been detected in the U.S. since late 2024. Over a quarter of these cases were diagnosed in March 2026 alone.
According to the CDC, all U.S. cases of clade I mpox — which are not linked — were in people who had either recently traveled to areas associated with the outbreak in Central and Eastern Africa or parts of Western Europe with more recent outbreaks, or, like the San Francisco case, were linked to travel.
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In other parts of the world, clade I has proven a more severe strain of mpox compared to the clade II strain that caused an outbreak in the Bay Area in 2022, and that’s still circulating at low levels. But SFDPH said officials are still determining whether clade I mpox causes more severe disease than clade II mpox in the U.S., and stress that the risk of exposure to mpox “is low for individuals who are not in higher‑risk groups.”
“While anyone can get mpox, most reported cases in the United States are among gay, bisexual and other men who have sex with men, as well as transgender persons who have sex with men,” the agency said.
A two-dose vaccine, which offers protection against both clade I and clade II, remains available for eligible people at higher risk of infection.
“This development reminds us just how important it is to be fully vaccinated against mpox if you are at risk,” said Dr. Susan Philip, San Francisco health officer.
“With summer travel and events quickly approaching, now is a great time to seek the mpox vaccine,” Philip said.
Keep reading for what we know about this new Bay Area case of clade I mpox, how mpox spreads, what symptoms to be aware of and who should get an mpox vaccine.
The mpox virus spreads through close contact with someone who is infected and causes mpox disease. As the name might suggest, the virus is related to the smallpox virus, but it’s generally less severe and much less contagious than smallpox, according to the California Department of Public Health. In addition to fever, chills, headache and muscle pain, mpox can cause a painful rash — also known as lesions — that appears on many parts of the body.
In 2024, the World Health Organization declared a clade I mpox outbreak that began in late 2023 in eastern and central Africa a global emergency. Historically, this strain has caused more severe illness and higher fatality rates than the other type of mpox, clade II.
Since Jan. 1, 2024, more than 53,000 clade I mpox cases and more than 200 deaths have been confirmed in several countries throughout Central and Eastern Africa, including the Democratic Republic of the Congo (which was originally the epicenter of the outbreak), Burundi, Central African Republic, Republic of the Congo, Rwanda and Uganda.
Since March 2025, over 30 countries have reported over 37,000 cases of the strain.
The first clade I mpox case outside the African continent was detected in Sweden in August 2024. In November of that year, the first U.S. clade I mpox case was confirmed in a Bay Area resident.
The 2022 mpox outbreak in the United States — which particularly affected gay and bisexual men, as well as trans and nonbinary people who have sex with men — was caused by clade II mpox, the less severe strain. Read more about the 2022 outbreak.
Wastewater data shows that four years after the initial 2022 outbreak, clade II of mpox is still occasionally detected in the Bay Area’s wastewater.
According to the CDPH, San Francisco has seen over 1,000 cases of clade II mpox since the 2022 outbreak, but the state’s most recent data shows the average of new cases has dropped to under two people a week.
Clade I cases in Central and Eastern African countries “at first spread through heterosexual intimate or sexual contact between adults, then spread likely occurred within households, including to children,” the CDC said.
But the agency notes that while the first cases outside that continent were primarily linked to travel to Central and Eastern African countries, as of late 2025 central Western European countries began reporting clade I mpox cases “among individuals who had no documented history of international travel” — cases which the CDC concludes were “likely related to intimate or sexual exposure among men who have sex with men.”
The CDC now “expect[s] additional cases” of clade I in Europe and the United States.
The mpox virus spreads through close — usually skin-to-skin — contact with someone who is infected. This could be direct contact with the infectious rashes or scabs someone with mpox develops, scabs, having intimate physical contact with someone who has mpox, such as kissing, cuddling or sex. Coming into contact with infected bodily fluids or items that have been touched by rashes or fluids from an infected person can also expose you to the virus.
The symptoms of clade I and clade II mpox are similar, SFDPH’s Janssen said, and they can often start as flu-like conditions, which is worth bearing in mind as the Bay Area enters respiratory virus season.
The mpox virus also appears as a rash or sores or spots that can resemble pimples or blisters on the skin anywhere on the body, including the face, inside the mouth, hands, feet, chest, genitals and anus.
These spots often start as red, flat spots that then become bumps before the bumps become filled with pus and turn into scabs when they break. These symptoms can be extremely painful. If you’re unsure about recognizing an mpox rash, the CDC has a photo guide.
Mpox can have a long incubation period — that is, the time between when you’re exposed to mpox and when you start to develop symptoms — that can range from three to 17 days, according to the CDC.
If you suspect you might have mpox symptoms — even if they’re subtle — see your health care provider right away or consult one of SFPDH’s clinics for mpox testing.
The vaccine currently available in the U.S. (brand name: Jynneos) is a two-dose series, with roughly a month between doses. Maximal immunity will build two weeks after your second dose. If you only got one dose previously, go ahead and seek out your second dose ASAP.
The vaccine “provides the best protection against the mpox virus and protects against both clade I and clade II,” according to a statement from the SFDPH.
The CDC recommends the two-dose mpox vaccine to gay and bisexual men and other men who have sex with men, as well as transgender, nonbinary or gender-diverse people who in the past 6 months have had:
The CDC’s vaccine recommendations also include anyone who has had sex at a commercial sex venue like a sex club or bathhouse. See the CDC’s full mpox vaccine eligibility recommendations.
San Francisco additionally recommends vaccination for anyone living with HIV, anyone taking PrEP or who’s eligible to take it and sex workers.
In 2024, the CDC updated its vaccination recommendations to extend to people traveling to countries with clade I outbreaks. The agency recommends getting both doses of the vaccine “if you anticipate experiencing any of the following” while traveling to these countries:
The mpox vaccine was also originally only available for people aged 18 and older, but in 2022, the Food and Drug Administration (FDA) issued an emergency-use authorization that allows providers to also give the vaccine to young people aged under 18 who are “determined to be at high risk” of infection.
If you have a regular health care provider, SFDPH recommends you ask them first about getting the mpox vaccine. Your vaccine will be free, but you may be charged a regular copay for seeing your provider.
If you’re eligible for the vaccine, your health insurance should cover the costs thanks to the CDC’s recommendations. If you don’t have a regular health care provider or insurance, SFDPH said you can visit one of these three recommended clinics in the city. You can opt to schedule an appointment or choose a walk-in clinic, depending on what works best for you.
(As with the COVID-19 vaccine, receiving an mpox vaccine won’t make you a public charge or affect any future immigration processes you may enter into, and you won’t be asked about your immigration status to receive the mpox vaccine.)
See a full list of mpox vaccine sites near you in San Francisco. SFDPH confirms that you don’t have to be a city resident to get vaccinated for mpox in San Francisco.
You can also find an mpox vaccine clinic near you using the state’s myturn.ca.gov site.
Some pharmacies offer mpox vaccination appointments online, along with other vaccines like COVID-19 and flu. But if you choose this route, you’ll be asked for insurance details — and it’s important to verify with your insurer ahead of time that they’ll cover the cost of an mpox vaccine at a pharmacy like CVS or Walgreens, as the out-of-pocket costs you’ll be quoted may be steep. If you find your insurance doesn’t fully cover the cost, SFDPH said you can seek your vaccine at one of their clinics, while supplies last.
If you get your health care through a health system like Kaiser Permanente, it’s unlikely you’ll be able to get your mpox vaccine covered by insurance at a pharmacy like CVS or Walgreens — the way you can’t get your COVID-19 or flu shot covered by Kaiser at a pharmacy either — and may have to seek it directly from a Kaiser provider.
If you’re able to make an appointment online at a pharmacy for your mpox vaccine, you should consider calling that location ahead of time to verify that they do indeed have supplies in stock.
This story includes reporting from KQED’s Carlos Cabrera-Lomelí and Nisa Khan.
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