Two people in California have been infected with a potentially more deadly strain of smallpox, which was acquired within the United States.
The Los Angeles County Department of Health confirmed this week that two unidentified residents in the county have tested positive for “Clade I” Mpox, which kills as many as one in 10 people it infects.
Individuals outside the United States did not travel to high-risk areas such as East Africa, meaning they acquired it locally. This is the first time Clade I has been acquired locally in the United States.
The first case, reported Tuesday, was a resident of nearby Long Beach, while the second case, reported Thursday, was a Los Angeles County resident.
Both patients were hospitalized but are now recovering at home, health officials said. No further details were revealed.
The Clade I strain is more dangerous than the Clade II variant, which is currently spreading in the United States and was behind the 2022 outbreak. Clade II has a fatality rate of less than three percent and has killed 63 Americans since the 2022 outbreak.
Health officials said the first type, which has a fatality rate of up to 10%, spreads more easily, “including through close personal contact,” such as massage, hugging and sex.
Six cases of Clade I Mpox have been reported in the United States among people who traveled to areas associated with the outbreak in Central and East Africa, according to the CDC, including a California resident who was infected last November. The agency said none of these cases were linked to each other.
The photo above from 2024 shows a patient in the Democratic Republic of the Congo infected with Mpox virus, formerly known as monkeypox
San Mateo County officials said at the time that the California resident had a mild illness last year.
“Although the overall risk of exposure to the public remains low, we take this very seriously,” Long Beach Mayor Rex Richardson said in a statement.
“This underscores the importance of continuous monitoring, early response and vaccination.”
Cases of type 1 smallpox in Africa are not closely tracked, but the latest estimates from the Centers for Disease Control and Prevention in late 2024 counted nearly 40,000 suspected cases in central and eastern Africa, specifically in the Democratic Republic of the Congo.
Smallpox, formerly known as monkeypox, is spread through close, intimate contact such as bodily fluids, sores, sharing bedding or clothing, kissing, having sex, coughing, or sneezing.
Symptoms “include a rash, unusual pimple-like sores or pus-filled blisters on the face, body and genitals, fever, chills, headache, muscle aches or swollen lymph nodes,” the Los Angeles County Department of Public Health said.
The Long Beach Department of Health and Human Services advised avoiding sex and intimate contact and seeking immediate medical help if individuals develop “unexplained rashes or lesions.”
The file image above shows red Mpox molecules inside the infected cell (blue)
In the Democratic Republic of the Congo, CDC officials said transmission was from “contact with dead or live infected wildlife” and “household contact often involving crowded households,” along with sexual contact.
The Long Beach Department of Health and Human Services said most patients recover on their own, although antiviral treatments “may be considered for individuals who are severely ill or at risk for disease.”
Anyone in the United States who is suspected of being exposed to smallpox in the past 14 days or who has certain sexual risk factors, such as gay or bisexual men, can receive two doses of the JYNNEOS vaccine to prevent infection.
People infected with HIV or who are immunocompromised are also eligible.