California mpox cases raise concerns. But health officials say the risk remains low
October 16, 2025
The confirmation of two clade I mpox cases in California, without travel links, marks a potential turning point in the U.S. outbreak landscape. While health officials stress that the public risk remains low, the emergence of possible local transmission is concerning, especially given reduced federal public health capacity amid the CDC shutdown. Clade I mpox, now widespread in Africa, poses broader risks across populations compared to the milder clade II strain. Early containment and cross-agency coordination are critical to preventing sustained transmission. This event underscores the continuing need for vigilance, testing, and well-resourced public health infrastructure.
Two mpox cases in California may represent the first evidence of local transmission of clade I mpox in the United States. Until now, all U.S. clade I cases were travel-related. The new infections in Long Beach and Los Angeles County, both requiring hospitalization but now recovering, show no confirmed links to international travel or to each other. Local health departments are actively tracing contacts and have administered precautionary vaccinations, but so far no additional infections have been identified.
Mpox, a viral illness in the same family as smallpox, has two known clades. Clade II caused the 2022 global outbreak, which primarily affected men who have sex with men and was largely contained through vaccination and community engagement. Clade I, however, is more transmissible and has caused significant outbreaks across eastern and central Africa, affecting children and broader demographics. The World Health Organization has warned that clade I poses a continuing global health threat.
The potential appearance of locally transmitted clade I mpox in the U.S. comes at a time of reduced federal preparedness. The government shutdown and staffing cuts at the Centers for Disease Control and Prevention limit the agency’s ability to coordinate surveillance, testing, and containment. Infectious disease experts have voiced concern that delayed federal response could weaken early containment efforts.
Although officials emphasize that the risk to the public remains low, this event highlights the importance of maintaining strong local and national surveillance systems. Early identification, transparent communication, and rapid vaccination of close contacts remain essential to preventing sustained transmission.
These California cases serve as a reminder that emerging pathogens do not respect borders. Continued vigilance, investment in public health infrastructure, and global collaboration are crucial to prevent isolated cases from evolving into wider outbreaks.