3 Cases of More Severe Mpox Strain Found in California — Here's What to Know

Three new cases of clade I mpox — the more severe strain of the disease formerly known as “monkeypox” responsible for outbreaks in Central and Eastern Africa — have been identified in Southern California, according to the California Department of Public Health.

In a statement on Friday, CDPH said they’d worked with local public health officials in Long Beach and Los Angeles County to identify these cases, which were not related to each other. “This is the first time clade I cases without a history of international travel have been reported in California or the United States,” CDPH said.

CDPH said that all three cases in Southern California “required hospitalization,” and the patients are now recovering.

The agency urged anyone who might be at heightened risk from mpox to seek out a free vaccine against the disease as soon as possible, if they haven’t already been vaccinated, noting that ” for either clade, vaccination lowers the chances of getting mpox and having severe disease.”

Jump straight to:

• Who’s eligible for an mpox vaccine in the Bay Area?
• Who can get clade I and clade II mpox?
• What are the symptoms of clade I and clade II mpox?

State health officials also said they’re conducting contact tracing around the Southern California cases and will continue to work with local health departments on surveillance — “and with the CDC as they are available during the federal government shutdown.”

On Monday, a spokesperson for CDPH said that the agency was continuing to work “with available staff at CDC” on their mpox response, but warned of “delays in coordination and communication” that “will put our communities at greater risk and reduce CDPH’s and local health jurisdictions’ ability to respond to a potentially larger outbreak.”

Dr. Julia Janssen, deputy director of the San Francisco Department of Public Health’s HIV/STI Prevention and Control Branch, confirmed that “thus far, we have had no clade I mpox cases reported in San Francisco, and we’re continuing to monitor the situation in Southern California closely.”

Keep reading for what you need to know about mpox amid news of these three new clade I mpox cases in the state.

What is clade I mpox?

As the name suggests, mpox is related to the smallpox virus but is generally less severe and far less contagious than smallpox, according to CDPH. 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.

Clade I mpox has caused widespread disease and even death in countries including the Democratic Republic of the Congo (DRC), which was the epicenter of the ongoing outbreak in 2024. It’s a different strain than clade II mpox, which is the kind that caused an outbreak in the Bay Area in 2022, and that’s been circulating at low levels since.

Who can get clade I — and clade II— mpox?

Anyone can get mpox, which spreads mainly through close physical contact, including sex.

But past clade II outbreaks in the U.S. have particularly affected gay and bisexual men, along with trans and nonbinary people who have sex with men.

And these new clade I cases in Southern California being unrelated to each other — and in people who hadn’t traveled to affected regions — now indicates “that person-to-person community spread of clade I mpox is occurring in California, primarily impacting communities of gay and bisexual men, and other men who have sex with men, as well as their social networks,” CDPH said.

According to the Centers for Disease Control and Prevention’s website, which was last updated on Sept. 15, only six cases of clade I mpox have been reported in the U.S. — all in people who had recently traveled to countries affected by a clade I outbreak. The first U.S clade I case was detected in San Mateo County in November 2024.

According to CDPH, the risk of clade I mpox to the general public remains low right now. “Casual contact, like one might have in an airplane, office, or store, is unlikely to spread mpox,” the agency said.

What should I know about the symptoms of mpox?

Mpox spreads through physical contact

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.

In 2024, UCSF infectious disease expert Dr. Peter Chin-Hong issued a reminder that infection still “requires close skin-to-skin contact or intensive household contact — so you can’t get it from Muni or from yoga, or from going to Trader Joe’s.”

“It’s still very hard to get mpox, even from somebody with active lesions,” he said.

Mpox symptoms don’t start straight away after exposure

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.

This period can range from as short as three days and as long as 17 days (almost three weeks), according to the CDC.

Mpox symptoms and affected areas can be varied

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 comes down from another COVID-19 wave.

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.

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. See more on what to do if you suspect you have mpox.

I’ve already got my mpox vaccine. Should I seek out a booster now?

There’s no current recommendation for a booster dose of the mpox vaccine.

Will the mpox vaccine protect me against both strains of mpox?

Yes, confirmed Janssen: “The mpox vaccine protects against both clades: clade I and clade II.”

Who’s eligible for a new mpox vaccine in the Bay Area?

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 be built two weeks after your second dose. If you only got one dose previously, go ahead and seek out your second dose ASAP.

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, or anticipate having:

• More than one sexual partner and/or
• A new diagnosis of one or more sexually transmitted infections.

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 full mpox vaccine eligibility recommendations from the CDC.

San Francisco additionally recommends vaccination for anyone living with HIV, anyone taking PrEP or who’s eligible to take it and sex workers. SFDPH also recommends it for anyone who has sex “at a large event in a geographic area where mpox virus transmission is occurring, or has a sex partner with any of the stated risks,” Janssen said earlier in 2025.

Will the mpox vaccine stop me getting mpox entirely?

Like the COVID-19 vaccine, the mpox vaccine can’t prevent all infections.

Janssen told KQED earlier this year that while fewer than 1% of people who are fully vaccinated have been diagnosed with the disease, “no vaccine is 100% effective” — “and while mpox infection after vaccination is rare, it does occur.”

But even if someone who’s fully vaccinated with Jynneos does get infected with mpox, she said, “those cases are typically mild.”

In other words, like the COVID-19 shot, the mpox vaccine makes it far more likely that any infection you get is far less severe than it would have been if you hadn’t been vaccinated.

And the difference between suffering from severe mpox versus a mild case can be considerable, as attested to by the “excruciating” symptoms reported during the early days of the 2022 U.S. outbreak, when most patients hadn’t yet been offered the mpox vaccine. ”

Travel and mpox vaccination

The CDC has updated its vaccination recommendations to extend to people traveling to countries with clade I and clade II outbreaks.

As of Sept. 15, these countries with clade I outbreaks include Burundi, Central African Republic, Democratic Republic of the Congo, Ethiopia, Kenya, Malawi, Mozambique, Republic of the Congo, Rwanda, South Sudan, Tanzania, Uganda and Zambia. Countries with new clade II outbreaks include Liberia and Sierra Leone.

The agency recommends getting both doses of the vaccine “if you anticipate experiencing any of the following” while traveling to these countries:

• Sex with a new partner
• Sex at a commercial sex venue, such as a sex club or bathhouse
• Sex in exchange for money, goods, drugs or other trade
• Sex in association with a large public event, such as a rave, party or festival.

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 under 18 who are “determined to be at high risk” of infection.

Where can I find an mpox vaccine near me?

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, you can find the mpox vaccine free at clinics around the Bay Area. 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.)

If you live in or near San Francisco:

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 in San Francisco to get vaccinated for mpox.

Mpox vaccination sites elsewhere in the Bay Area and California:

Find an mpox vaccine clinic near you using the state’s myturn.ca.gov site.

Getting an mpox vaccine at a pharmacy:

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 supply in stock.

This story includes reporting from KQED’s Billy Cruz, Carlos Cabrera-Lomelí and Nisa Khan.