California Reports First Severe Clade I Mpox Case: CDC Updates on Public Health Risks

US Confirms First Case of Severe Mpox Strain

The first known case of a more severe strain of mpox, called clade I, has been reported in California, according to the US Centers for Disease Control and Prevention (CDC). The public’s risk from this strain remains low, the agency stated.

The diagnosed individual had recently traveled from Eastern Africa, where there is an ongoing mpox outbreak. They received treatment at a local facility and have since been released. Their symptoms are improving, and they are isolating at home. The CDC and the state health department are tracking potential contacts.

Clade II mpox has been present in the US since large outbreaks in 2022 and 2023. Recently, Africa has seen an increase in clade I mpox cases, which can lead to more severe illness.

So far, all recent travel-related clade I cases outside Africa have been linked to subclade Ib, with no reported deaths. Available data indicates these cases generally result in mild disease.

The World Health Organization (WHO) reports that mpox cases in Africa are rising, primarily in the Democratic Republic of Congo, Burundi, and Uganda. On November 22, the WHO will hold a meeting to determine if the current outbreak remains a public health emergency of international concern.

Initial symptoms of mpox may include flu-like signs such as fever, chills, exhaustion, headache, and muscle weakness. These symptoms are often followed by a painful or itchy rash that develops into raised lesions, which scab over and heal over weeks.

To protect against mpox, the CDC advises staying away from people showing symptoms and from contaminated materials like clothing and personal items. Those eligible should receive two doses of the mpox vaccine.