Building the Future of Biodefense

Recommendation: This new H5N1 case in Cambodia does not change PHC's recommendations for organizations. No human-to-human spread of avian influenza has been detected. Organizations should follow the recommendations provided in the PHC analysis on 1/10 and 2/13, including lowering barriers to seasonal flu vaccines for their employees. Employees should avoid live-animal markets and not have contact with or consume diseased poultry.

Situation: Cambodia confirmed its 16th H5N1 human case in a 3-year-old child from the Kampong Speu Province. The child is currently receiving intensive treatment. It was reported that chickens and ducks at the child's house and neighboring houses had been sick and dying for about a week before the child became sick. Health officials distributed Tamiflu to close contacts and conducted health campaigns among residents in affected villages. [Confidence: Very High]

Recommendation: Organizations can support employees in obtaining mpox vaccinations by providing flexible work schedules. Information on the availability of mpox vaccines and treatment can also be included in employee wellness communication.

Situation: California detected an mpox clade 1 case in a Long Beach resident. The individual did not have any recent travel history and was hospitalized. This Long Beach case is the 1st ever detection of a locally acquired clade 1 case in the US, suggesting undetected community transmission may be ongoing. 6 imported mpox clade 1 cases with international travel history were previously reported in the US so far, with 2 in California, and then 1 case each in Massachusetts, New York, Georgia, and New Hampshire. The 2 other imported mpox clade 1 cases in California were reported in September 2025 in an individual who resided in Riverside County and in November 2024 in an individual who received treatment in San Mateo County (see PHC alerts on 9/19 and 11/18/2024). Long Beach reported 6 other mpox cases so far this year, but none were clade 1. Health officials stated that the risk to the public remains low, and further investigation and contact tracing are ongoing to determine if there are additional cases in the area. [Confidence: Very High]

Recommendation: Sporadic cases of locally acquired dengue have been reported in California, but it is generally rare. The peak mosquito season in Los Angeles County is from June to November, with warm weather prolonging the season. Organizations should reduce mosquito populations at their facilities by eliminating standing water. Employees can take steps to prevent mosquito bites by wearing protective clothing, using insect repellent, and eliminating standing water near their homes.

Situation: Health officials confirmed a locally acquired case of dengue in a resident of the San Gabriel Valley, Los Angeles County, with no history of domestic or international travel. This is the 1st locally acquired case reported in Los Angeles County this year. Enhanced vector surveillance activities were implemented, including increased mosquito trapping and monitoring activities. The overall risk of sustained local dengue transmission in the county remains low, but this case highlights the presence of infected mosquitoes in the area. In 2024, 14 locally transmitted dengue cases were identified in the county. [Confidence: Very High]

Recommendation: Local chikungunya transmission is very rare in the mainland US, with 13 cases detected in Florida and Texas in 2014-15, though it more commonly occurs in some US territories. Before this detection, no cases had been reported in the US states and US territories since 2019. Organizations in Nassau County, New York, should reduce mosquito populations at their facilities by eliminating standing water. Employees can prevent mosquito bites by wearing protective clothing, using insect repellent, and eliminating standing water near their homes.

Situation: New York confirmed its 1st ever locally acquired chikungunya case this week, an update to the PHC alert on 9/26. The individual resides in Nassau County on Long Island. The exact location of exposure is not known at this time, but it was classified as locally acquired based on current information. The Aedes albopictus mosquito, a vector of chikungunya, is present in downstate New York. For chikungunya transmission to occur, the mosquito must first bite an infected individual before transmitting the disease to others. 3 and 8 imported chikungunya cases were reported in the state (outside of New York City) and in New York City, respectively, so far this year. Chikungunya has not been detected in any New York mosquito samples yet. Health officials stated the current risk is very low, especially as mosquito activity is on the decline with decreasing temperatures. [Confidence: Very High]