Health officials in multiple states are reporting detections of mpox, including the first known finding of clade I in Hawaii wastewater and ongoing low-level circulation of clade II in the San Francisco Bay Area. As of late May 2026, public health agencies across California, Hawaii, and Wisconsin are advising individuals at higher risk to consider vaccination.
Current Situation and Case Data
California and the Bay Area
Wastewater monitoring in the Bay Area continues to detect clade II mpox, four years after the initial 2022 outbreak. The California Department of Public Health (CDPH) reported that San Francisco has recorded over 1,000 cases of clade II mpox since 2022, with current data showing an average of fewer than two new cases per week.
On a separate development, a San Francisco resident was hospitalized after being diagnosed with clade I mpox. The individual was unvaccinated and had close contact with an international traveler. This is the seventh clade I case identified in California. The first case in the state was detected in San Mateo County in November 2024, with subsequent cases in Los Angeles County in October 2024 and January 2025.
Regarding overall case rates, California officials report that current clade II case rates are higher than in the preceding two years. The current weekly case rate is 14.5, compared to 3.4 for the comparable period in 2025 and 5.8 in 2024. Most recent infections have occurred in individuals who were not vaccinated.
Hawaii
The Hawaii Department of Health (DOH) reported that a wastewater sample from Oahu tested positive for clade I mpox. The sample was collected on April 13 from a wastewater treatment facility at Joint Base Pearl Harbor-Hickam, which serves on-base military housing and public sites including the Pearl Harbor National Memorial Museum. The DOH received initial detection notice on April 20, with confirmatory results on April 24. A subsequent sample from the same facility on April 20 tested negative. As of April 24, samples from major civilian wastewater facilities on Oahu have tested negative. Officials stated the risk to the general public is low and no clinical case has been identified in Hawaii.
Wisconsin
The Wisconsin Department of Health Services (DHS) reported five confirmed mpox cases in the state as of May 26, 2026. Cases occurred in northern and southeastern Wisconsin. Nationally, 535 confirmed mpox cases were reported across the U.S. as of May 3, 2026.
Virus Strains and Transmission
Mpox is caused by two types of virus: clade I and clade II. Both spread through close, usually skin-to-skin contact with an infected person. Transmission can occur through direct contact with infectious rashes or scabs, intimate physical contact (including kissing or sex), or contact with infected bodily fluids or contaminated items. Officials state the virus does not spread through air or casual contact.
Clade I Specifics
The Centers for Disease Control and Prevention (CDC) reported that clade I cases in Central and Eastern African countries initially spread through heterosexual intimate or sexual contact between adults, then likely spread within households, including to children. The CDC noted that while initial cases outside Africa were linked to travel to those regions, by late 2025 central Western European countries began reporting clade I mpox cases among individuals with no documented international travel history. The CDC concluded these European cases were likely related to intimate or sexual exposure among men who have sex with men. The CDC now expects additional clade I cases in Europe and the United States.
Health officials state that clade I infections may cause more severe illness and spread more easily through close personal contact than the clade II strain. There are no confirmed cases in the U.S. of the mpox variant causing the current outbreak in Africa, which officials describe as a different variant.
Clade II Specifics
The California Department of Public Health reports that clade II continues to be detected occasionally in Bay Area wastewater.
Symptoms
According to the San Francisco Department of Public Health, symptoms of clade I and clade II mpox are similar and often begin with flu-like conditions. The virus appears as a rash, sores, or spots resembling pimples or blisters that can occur anywhere on the body including the face, mouth, hands, feet, chest, genitals, and anus. These spots typically progress from red, flat spots to bumps that fill with pus and eventually form scabs.
The CDC reports the incubation period ranges from 3 to 17 days.
Additional symptoms reported by health agencies include:
- Fever
- Chills
- Headache
- Muscle aches
- Swollen lymph nodes
The rash can be painful. The CDC provides a photo guide for rash identification.
Vaccination
Vaccine and Eligibility
The Jynneos vaccine available in the U.S. is a two-dose series administered approximately one month apart, with maximal immunity developing two weeks after the second dose. The San Francisco Department of Public Health stated the vaccine provides protection against both clade I and clade II mpox. Health officials state the vaccine lowers the chance of infection and severe illness from either strain.
The CDC recommends the two-dose vaccine for:
- Gay and bisexual men and other men who have sex with men
- Transgender, nonbinary, or gender-diverse people who in the past 6 months have had multiple sexual partners or a new STI diagnosis
- Anyone who has had sex at commercial sex venues
San Francisco additionally recommends vaccination for:
- Anyone living with HIV
- Anyone taking PrEP or eligible for it
- Sex workers
In 2024, the CDC updated recommendations to include people traveling to countries with clade I outbreaks who anticipate specific activities including sex with new partners, sex at commercial venues, sex in exchange for goods or services, or sex associated with large public events.
The vaccine was originally approved for people aged 18 and older. In 2022, the FDA issued emergency-use authorization allowing providers to administer it to people under 18 determined to be at high risk of infection.
Access to Vaccination
Individuals with regular healthcare providers are advised to inquire about vaccination through them, with vaccines being free though copays may apply for provider visits. Health insurance should cover vaccine costs for eligible individuals per CDC recommendations.
Those without regular providers or insurance can visit SFDPH-recommended clinics in San Francisco, with appointment or walk-in options available. San Francisco residents and non-residents can access vaccination through SFDPH sites or the state's myturn.ca.gov website. Some pharmacies offer mpox vaccination appointments, though individuals should verify insurance coverage as out-of-pocket costs may be significant.
Vaccination does not affect immigration status or processes, and immigration status is not required for vaccination.
Public Guidance
Health officials state mpox is unlikely to spread through casual contact in settings like planes, offices, or stores.
Individuals with suspected symptoms are advised to consult a healthcare provider or local health department clinics for testing. Those exposed to mpox are advised to get vaccinated before symptoms develop. Infected individuals should stay home and avoid contact until the rash has healed.
The Hawaii Department of Health encourages people at higher risk to consider vaccination with two doses of the JYNNEOS vaccine if not already protected. The Wisconsin Department of Health Services encourages individuals at higher risk of exposure to discuss vaccination with a healthcare provider and recommends knowing mpox symptoms, monitoring one's own and partner's body for rashes or skin lesions, and having open conversations with partners about mpox, sexually transmitted infections, and HIV.