California Reports First Clade I Mpox Cases
Three individuals in California have contracted clade I mpox, a more serious variant of the virus previously known as monkeypox. This is the first recorded instance of this strain spreading within the United States, according to health officials on Friday.
The cases, which are not connected, were identified in Long Beach and Los Angeles County. Notably, all patients had not traveled outside the country recently. They were hospitalized but are now on the mend, as reported by the California Department of Public Health.
Mpox is a viral infection that typically starts with symptoms resembling the flu, including fever, chills, and muscle pain. Afterward, patients often develop a rash that begins as small bumps, morphing into fluid-filled blisters before they eventually form scabs.
This virus has two major genetic groups, known as clades. Clade I mpox has led to widespread disease and fatalities in some regions of central and east Africa, with the Democratic Republic of the Congo being hit hardest. Clade II was responsible for the US outbreak in 2022, though it’s circulated at lower levels since then.
Seth Blumberg, an associate professor at the University of California, San Francisco, expressed the need for careful evaluation regarding the presence of clade I. He noted, “I don’t think the historical results we’ve seen from Africa are directly translatable, but we need to monitor these cases closely.”
Dr. Rita Nguyen, assistant state public health officer, mentioned in a statement that “clade I mpox cases can be severe” and emphasized that the severe disease risk is notably higher for individuals with compromised immune systems.
She underscored the importance of vaccination, urging people who may be at risk to get both doses of the mpox vaccine.
Mpox can spread through close physical contact, including sexual encounters. Past clade II outbreaks primarily impacted gay and bisexual men, as well as transgender or non-binary individuals engaging in sexual activity with men. California’s public health department now believes that person-to-person transmission of clade I is occurring, mainly affecting these communities.
The first identified case in Long Beach was announced on Tuesday.
Previously, the Centers for Disease Control and Prevention (CDC) had reported six clade I cases in the US, all linked to international travel, with the initial case detected in San Mateo County in 2024. Health officials maintain that the overall risk to the public remains low, suggesting that casual contact in places like public transport or offices is unlikely to facilitate virus spread.
The Jynneos vaccine is effective against both clade I and clade II mpox varieties. It is administered in two doses, spaced a month apart, with full immunity expected two weeks post the second dose. Currently, no booster shots are recommended.
While vaccination doesn’t entirely eliminate the risk of contracting mpox, experts believe it can lessen the severity of the illness. Blumberg remarked on the protective benefits of vaccines, asserting that they can help prevent severe disease and decrease the likelihood of requiring advanced medical care.
The CDC has indicated uncertainty about the duration of vaccine protection and whether it might diminish over time. The agency is currently analyzing data and conducting studies to better understand how the Jynneos vaccine performs amid the ongoing mpox outbreak and the longevity of its protective effects.
