Three Californians have been hospitalized with severe cases of mpox, marking the first time the more dangerous Clade 1 variant has spread locally within the United States without any link to international travel. This development has set off alarm bells among public health officials, who are now racing to contain what could become a significant public health threat if not swiftly addressed.
The three cases, confirmed between October 17 and October 21, 2025, involved residents of Los Angeles County and Long Beach. According to the California Department of Public Health, all three individuals required hospitalization but have since recovered and are now isolating at home. What makes these cases particularly unsettling is the absence of any recent overseas travel—a detail that strongly suggests the Clade 1 variant is now circulating within local communities.
“The confirmation of a third case with no travel history raises concerns about possible local spread in Los Angeles County,” Dr. Muntu Davis, the Los Angeles County health officer, stated in a press release, as reported by ABC News. “We’re working closely with our partners to identify potential sources and understand how this potentially more serious type of the mpox virus may be spreading.”
Mpox, formerly known as monkeypox, is a viral disease caused by the monkeypox virus—a close cousin of the smallpox virus. The disease is divided into two main clades: Clade 1, which is historically found in central and western Africa and is associated with more severe symptoms and higher mortality, and Clade 2, which was responsible for the 2022 global mpox outbreak. While Clade 2 generally causes milder illness, Clade 1 is notorious for its aggressive progression and increased risk of complications, especially among immunocompromised individuals.
Until now, all previous Clade 1 mpox cases in the U.S. were linked to international travel, typically to regions where the virus is endemic. According to the Centers for Disease Control and Prevention (CDC), the initial U.S. case of Clade 1 mpox was identified in San Mateo County in 2024, and five subsequent cases were also travel-related. The current trio of cases, however, stands out for having no such links, raising the specter of undetected local transmission.
Health officials have not found any epidemiological connections between the Long Beach case and the two Los Angeles County cases. This lack of linkage suggests either multiple introduction points or ongoing, undetected spread within the community. As Dr. Kelly Johnson, an infectious disease expert at the University of California, San Francisco, told local media, “The emergence of Clade 1 locally is concerning, but with appropriate public health measures, transmission can be limited.”
Mpox typically begins with symptoms that mimic the flu—fever, chills, muscle pain, swollen lymph nodes, and fatigue. Within days, a distinctive rash appears, often spreading to the hands, feet, face, and genital area. The rash progresses from small raised marks to fluid-filled blisters and eventually scabs. Clade 1 cases, in particular, are more likely to result in severe complications such as secondary infections, respiratory distress, and, in rare cases, death. The CDC notes that the highest risk of severe disease and hospitalization is among people with weakened immune systems.
Transmission of the virus occurs primarily through intimate physical contact, including sexual activity, but can also happen via respiratory droplets during prolonged face-to-face interactions or by sharing personal items like bedding or clothing. In California, state health authorities have observed that transmission rates are highest among gay and bisexual men, as well as transgender and non-binary individuals who have sex with men.
In response to the recent cases, California’s public health apparatus has swung into action. Enhanced surveillance and targeted testing are now underway to identify additional infections and map transmission networks. Vaccination clinics have been expanded, focusing on at-risk populations such as men who have sex with men and immunocompromised individuals. Public education campaigns are ramping up, aiming to inform communities about symptoms, prevention strategies, and the importance of seeking medical care at the first sign of illness.
The JYNNEOS vaccine, a two-dose regimen approved by the Food and Drug Administration to prevent both smallpox and mpox, is at the heart of these prevention efforts. “It’s critical to protect yourself by getting both doses of the mpox vaccine if you or your sex partner(s) may be at risk for mpox,” Dr. Rita Nguyen, assistant state public health officer, emphasized in a statement. Full protection develops about two weeks after the second dose, which is administered four weeks after the first. Seth Blumberg, an associate professor of medicine at UC San Francisco, added, “Vaccines can prevent the severity of disease. If you were to get mpox, you would be less likely to need advanced care.”
Despite these efforts, challenges remain. Approximately 40% of California’s at-risk population has been vaccinated against mpox, leaving a significant portion still vulnerable. Vaccine hesitancy, limited supplies, and cultural stigma—particularly in communities most affected by the outbreak—pose ongoing hurdles. Moreover, the similarity of mpox symptoms to other viral illnesses can delay diagnosis and impede timely intervention.
Statistically, the situation is evolving rapidly. Los Angeles County alone has reported over 100 mpox cases in 2025, a sharp increase from the near-zero case levels seen in 2024. The state’s health officials are bracing for the possibility of more cases as they intensify contact tracing and vaccination outreach. Hospital preparedness is also a focus, with protocols being updated to ensure facilities can safely manage severe mpox infections without compromising care for other patients.
According to BBC News, the CDC maintains that the general risk to the public remains minimal at this time, with casual transmission in workplaces or on public transport considered unlikely. Still, the agency stresses the importance of vigilance, particularly for those at higher risk. Preventive guidance includes avoiding close skin contact with symptomatic individuals, practicing good hygiene, and seeking medical attention for any suspicious rash or illness.
Looking ahead, health departments plan to monitor mpox trends closely, adapting their strategies as new information emerges. Ongoing research into improved vaccines and treatments is underway, with hopes of enhancing preparedness for future outbreaks. Collaboration with federal agencies and international partners will be crucial, given the global nature of infectious diseases like mpox.
The sudden appearance of severe, locally acquired Clade 1 mpox cases in California is a stark reminder of the unpredictable nature of infectious diseases. While the risk to the general public remains low, the situation demands continued vigilance, scientific innovation, and a compassionate public health response to protect vulnerable groups and prevent further spread.
