California Reports Community Spread of New Mpox Type

The California Department of Public Health (CDPH) and local health officials in the City of Long Beach and Los Angeles County, have identified three unrelated cases of clade I mpox in Californians who did not report recent travel outside the U.S. These cases indicate 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. Prior cases of clade I mpox in the U.S. have been associated with international travel to areas where clade I mpox is circulating.

All three cases required hospitalization and are now recovering. Local health departments and CDPH are conducting enhanced surveillance and contact tracing to identify any additional cases and prevent further transmission. Currently, the risk to the public remains low.

“As we continue to monitor the situation, it is crucial for Californians to stay informed and take preventive measures, especially persons who are more likely to be exposed to mpox,” said Dr. Rita Nguyen, CDPH assistant state public health officer. “Clade I mpox cases can be severe. Risk of severe disease and hospitalization are highest for people with weakened immune systems, so it’s critical to protect yourself by getting both doses of the mpox vaccine if you or your sex partner(s) may be at risk for mpox.”

Mpox is an infection caused by the monkeypox virus. Two types of mpox, clade I and clade II, exist. Both types cause similar symptoms and can be prevented using the same methods and vaccine. Mpox mainly spreads through close contact to a person who has mpox infection. This includes:

• Intimate physical contact such as massages, cuddling, or sex (oral, anal, or vaginal)
• Direct skin-to-skin contact with the rash, scabs, or body fluids that touched sores
• Sharing a living space or personal items with someone who has mpox
• Spread from a pregnant person with mpox to the fetus or baby

Casual contact, like one might have in an airplane, office, or store, is unlikely to spread mpox.

Clade I mpox is different from clade II mpox, which has been circulating in California and the U.S. since 2022. Mpox symptoms in clade I cases can be severe. The risk of severe disease and hospitalization is highest for people with weakened immune systems. Both clades may present flu-like symptoms, followed by a rash, and are diagnosed through laboratory testing. For either clade, vaccination lowers the chances of getting mpox and having a severe case of the disease. Two doses of the mpox vaccine are recommended while boosters are not. 

CDPH said health care providers should incorporate assessments for mpox risk and vaccination status at all sexual health visits, and test patients with compatible signs and symptoms, regardless of vaccination status or previous infection.