New Deadly Strain of Mpox Virus Discovered in California

A new and potentially more lethal strain of the Mpox virus has been identified in California, marking a significant health concern. The Los Angeles County Department of Health confirmed that two local residents tested positive for the ‘Clade I’ variant, which is associated with a mortality rate of up to 10 percent. This development highlights the strain’s ability to spread more easily and its emergence within the United States.

Both individuals infected with Clade I Mpox had not traveled to high-risk regions such as East Africa, indicating that they contracted the virus locally. The first case was reported on October 15, 2025, involving a resident of Long Beach, followed by the second case from a nearby area. Health officials stated that both patients were hospitalized but are now recovering at home. Specific details about the patients have not been disclosed.

The Clade I strain poses a greater threat compared to the Clade II variant, which has been circulating in the U.S. since the 2022 outbreak. Clade II has a significantly lower fatality rate of less than three percent, accounting for 63 deaths since the outbreak. In contrast, Clade I is characterized by its increased transmissibility, spreading through close personal contact, including intimate activities.

According to the Centers for Disease Control and Prevention (CDC), there have been six reported cases of Clade I Mpox in the U.S. among individuals who traveled to regions with known outbreaks in Central and East Africa. These cases, including one from California in November 2024, were not linked to one another, suggesting that the current infections may represent a new transmission chain.

Long Beach Mayor Rex Richardson commented on the situation, stating, “While the overall risk of exposure to the public remains low, we are taking this very seriously. This underscores the importance of continued surveillance, early response, and vaccination.”

The CDC’s estimates indicate nearly 40,000 suspected cases of Mpox in Central and East Africa, particularly in the Democratic Republic of the Congo (DRC). The virus, previously known as monkeypox, spreads through intimate contact, sharing personal items, and respiratory droplets. Symptoms include rash, fever, chills, and swollen lymph nodes.

The Long Beach Department of Health and Human Services has advised residents to avoid intimate contact and seek medical attention immediately if they experience unexplained rashes or lesions. In the DRC, transmission occurs through contact with infected animals and crowded households, along with sexual interactions.

Most individuals infected with Mpox recover without severe treatment, but antiviral medications may be necessary for those at risk of developing severe illness. The JYNNEOS vaccine is available for individuals who suspect exposure to the virus within the last 14 days or who have certain risk factors, including gay or bisexual men and those with compromised immune systems.

As health authorities monitor the situation closely, public awareness and preventive measures remain essential to mitigate the spread of this new strain of Mpox.