California Governor Gavin Newsom announced on December 18 that California has entered a state of emergency due to the outbreak of avian influenza, also known as Bird Flu (H5N1). Since April 2024, the Centers for Disease Control and Prevention (CDC) has reported a total of 61 confirmed or suspected cases of avian influenza in the United States, with 34 cases in California, but no evidence of human-to-human transmission. Newsom stated that California’s actions are taken as a preventive measure.
On the 18th, the CDC confirmed the first case of a severe illness related to the H5N1 virus. The patient in Louisiana was infected with the D1.1 genetic type of the virus, which has been recently spreading among wild birds/poultry in the United States, with human infections also reported in Canada and Washington state. However, this differs from the B3.13 genetic type detected in sporadic cases in cattle, poultry, and several states.
The case manifested on the 13th and it has been established that the patient had contact with sick and dead chickens in a backyard flock. The CDC recommended preventive measures include “avoiding contact” as the virus can be present in the saliva, mucus, and feces of infected birds. The sporadic severe cases of avian influenza come as no surprise, the CDC said, as H5N1 has caused fatalities in previous years without inter-human transmission; the Louisiana case does not change the CDC’s assessment of “lower risk” concerning avian flu.
According to ABC’s report on the 18th, the 65-year-old patient had underlying conditions and was experiencing a severe respiratory illness related to avian influenza. The CDC noted that previous avian flu patients had mild conditions and recovered after receiving antiviral treatment. Almost all confirmed cases were directly linked to contact with infected cattle or poultry, including unpasteurized milk or raw cow’s milk.
A federal directive issued by the U.S. Department of Agriculture last week mandates the collection of raw milk samples nationwide for avian influenza testing. Previously, the virus was discovered in raw milk samples from a California farm, prompting a recall of all milk and quarantine measures.
Newsom stated, “This declaration of emergency is a targeted action intended to ensure that government agencies have the resources and flexibility needed to respond swiftly to the epidemic.” With California boasting the largest testing system in the U.S., Newsom emphasized that while the public’s risk remains low, all necessary measures will be taken to prevent the virus from spreading. According to the press release, the H5N1 avian influenza virus was first discovered in wild birds in South Carolina in January 2022; later in California’s wild birds in July of the same year; and in March 2024, Texas and Kansas reported outbreaks in cattle. On August 30, 2024, a cow in central California was confirmed to be infected with the avian influenza virus.
In a report by CBS on the 11th, a child in Marin County, California, developed a fever and vomiting after consuming unpasteurized milk, suspected to be related to avian influenza. The child has since recovered, and no other family members were affected, indicating no human transmission.
According to MedPage Today’s report on the 16th, initial testing of the child in Marin County revealed the presence of influenza A virus. Subsequent testing by California laboratories and the CDC yielded inconclusive results, unable to confirm whether the detected influenza A virus was H5N1 (avian influenza) or seasonal flu due to low levels of viral RNA. Kevin Griffis, Director of Communications at CDC, stated, “Samples tested negative for all flu targets.” Health officials in Marin County noted that the virus levels in the initial test samples were already low and could have dropped to undetectable levels by the time they reached the CDC lab.
Reported by the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota on the 17th, Tim Mastro, Deputy Director of Communications at the Delaware Department of Health and Social Services, stated that Delaware promptly contacted the CDC after identifying a suspected H5N1 patient during routine surveillance. After multiple tests, the CDC could not confirm the case.
Regarding animals and birds, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed seven cases of avian influenza in dairy cows, bringing the total infected dairy cows in California to 645, with a national count of 860 cases in 16 states. APHIS also reported H5N1 cases in other animals: one turkey at a chicken farm in Barron County, Wisconsin; one each of house mice and domestic cats in Cache County, Utah; one mountain lion each in Arizona and Washington state; and one domestic cat in San Bernardino County, California.