San Francisco confirms first Clade I mpox case among unvaccinated local residents.

San Francisco has officially confirmed its first case of the more dangerous Clade I mpox strain, marking a significant shift in the virus's epidemiology on the West Coast. City health officials report that the patient is an unvaccinated adult who was hospitalized but is currently recovering after close contact with someone who traveled internationally. This specific infection is not an isolated incident, as other California cities, New York, and various other jurisdictions have now documented similar cases without any history of international travel.

Health authorities indicate that mpox, a virus related to but milder than smallpox, is primarily spreading locally among gay and bisexual men with no known current links to Africa where Clade I remains endemic. Symptoms typically begin with fever, swollen lymph nodes, body aches, and extreme fatigue before progressing to a painful rash. This rash evolves through distinct stages from flat spots to firm bumps, pus-filled blisters, and finally scabs, a process that can span several weeks.

The primary concern regarding Clade I is its historical severity, having killed up to ten percent of untreated patients in Africa compared to fewer than three percent for Clade II in the United States. While experts believe US medical infrastructure would likely reduce mortality rates further, officials maintain close surveillance on the spread. Dr. Susan Philip, the city health officer, stated that while Clade I cases remain rare nationally, Clade II infections continue to occur within San Francisco and throughout the state.

By March, the Centers for Disease Control and Prevention reported fifteen total Clade I cases in the United States, with four diagnosed in that single month. Every identified patient was recovering, and all had either traveled to Central or Eastern Africa, visited Western Europe where newer outbreaks are occurring, or had contact with someone who did. Federal officials anticipate that additional cases will likely emerge in Europe and the US as the virus continues to circulate.

Transmission occurs through skin-to-skin contact, including sexual activity, hugging, kissing, and sharing bedding or towels. The virus can also pass from pregnant individuals to their fetus or newborn, and from animals to humans via bites or fluid contact, though these routes are not fueling the current outbreak. Scientists have not yet determined if the virus spreads through semen, vaginal fluid, urine, or stool. Officials advise travelers heading to Clade I outbreak zones who plan to have sex with a new partner to receive two doses of the JYNNEOS vaccine, regardless of their sexual orientation or gender identity.

Symptoms typically emerge one to three weeks following exposure to the virus. This extended incubation period allows infected individuals to travel and engage in intimate contact while remaining asymptomatic. Once the rash finally appears, patients describe the lesions as agonizingly painful. Swallowing, walking, or even sitting becomes unbearable when these sores develop. In severe instances, bacterial infections can turn the sores into a sepsis threat. Some patients require hospitalization for pain management, intravenous fluids, and antibiotics.

Scarring stands as one of the most debilitating consequences of the infection. Deep lesions often leave permanent pitted scars on the genitals, face, or corneas. Vision loss becomes a risk if the eyes sustain damage from these wounds. Unlike chickenpox, mpox lesions heal slowly and frequently leave disfiguring marks for life. Immunocompromised individuals face another hidden danger during this outbreak. People with untreated HIV confront much higher risks of severe disease or death. Most fatal Clade I cases in Africa have occurred among people with underlying immune problems.

Men who have sex with men should consult their doctors about receiving the vaccine. Trans, nonbinary, queer, and gender non-conforming individuals also need to discuss vaccination with medical professionals. San Francisco health officials issued specific travel advisories for this group. They recommend vaccination for anyone planning travel to a country where Clade I mpox spreads. Officials state that travelers who may have sex with a new partner should get the shot. This guidance applies regardless of sexual orientation or gender identity.