Mpox strain that may be more severe appears to spread locally in U.S. for first time

Local Transmission of Severe Form of Mpox Reported in California

The first cases of a more severe form of mpox without known travel history have been reported in California, alarming health officials. The Los Angeles County Department of Public Health confirmed an adult recovering at home after being hospitalized for clade I mpox, a strain known to cause severe illness and death, with no recent travel to affected regions in Africa. This marks the second locally acquired case of clade I in the county, following a similar report by the Long Beach Department of Health and Human Services.

Clade I vs. Clade II Mpox

Compared to clade II mpox, which caused the 2022 global outbreak, clade I is more likely to result in severe illness and death. Fatality rates for clade I range from 1% to 10%, higher than the 1% to 4% range for clade II. Clade I is also being reported in more children in the Democratic Republic of the Congo.

Spread and Prevention

The virus spreads through close contact with symptomatic individuals, particularly during sexual activity. The health department warns of transmission through close person contact and sharing personal items. Groups at higher risk, such as gay, bisexual, or other men who have sex with men, are advised to take preventative measures. Early detection, testing, and vaccination, particularly with the JYNNEOS vaccine, are crucial in controlling the spread of the virus.

Symptoms and Diagnosis

Both clade I and clade II mpox present with flu-like symptoms followed by a rash, usually appearing within 21 days of exposure. Rashes from clade I tend to cover more of the body, including the face and torso, while those from clade II may not cover the entire body.