By Lisa Schnirring
In an update yesterday on scientific investigations related to H5N1 avian flu activity, the Centers for Disease Control and Prevention (CDC) said genetic sequencing had identified the D1.3 genotype in a sample from an Ohio poultry culler whose infection was reported in the middle of February.
Also, the CDC reported serology findings from the investigation into a January H5N1 infection in a San Francisco child whose exposure to the virus remains unknown.
In other developments, the US Department of Agriculture (USDA) today announced new funding to battle avian flu in poultry, as its Animal and Plant Health Inspection Service (APHIS) confirmed more H5N1 detections in poultry from four states.
First known illness involving D1.3 genotype
In the early months of 2025, Ohio’s commercial poultry sector emerged as one of the worst affected by H5N1 outbreaks, and the poultry worker had prolonged contact with birds that had been sick. He was hospitalized with both respiratory and nonrespiratory symptoms. The patient had initially tested negative on upper-respiratory samples but was positive on lower respiratory tract sampling.
The CDC said sequencing shows the virus is a clade 2.3.4.4b virus of the D1.3 genotype, which like the D1.1 genotype descended from the A3 genotype that was introduced to North America in 2022 and has since reassorted with North American wild bird avian flu viruses. D1.1 has been circulating in wild birds and poultry and recently jumped to dairy cattle in Nevada and Arizona. It has also been implicated in a few human infections, two of them severe and one fatal.
Genetic analysis of the D1.3 virus didn’t identify any markers that would impact the effectiveness of antivirals or candidate vaccine viruses, the CDC said, adding that it did not see any changes that would allow the virus to more easily adapt to or spread among mammals. Efforts to isolate the live virus are still underway.
Serology in California probe rules out human-to-human spread
In another update, the CDC said its scientists have completed serology testing on blood samples from close contacts of a San Fransico child whose mild illness from an undetermined source was first announced in February.
The child’s blood had antibodies to H5N1, but testing on samples from the child’s close contacts were negative for previous infection with the virus, suggesting that none of them were infected.
“These findings are reassuring,” the CDC said, noting that so far, no human-to-human H5N1 transmission has been detected in the United States.
In its report, the CDC also spotlighted two recently published ferret studies that found pre-existing antibodies from earlier infection with the 2009 H1N1 seasonal flu virus might provide some protection against H5N1. One of the two studies, published this week in The Lancet Microbe, also found that the ferrets with previous exposure to H1N1 were less likely to pass the virus to animals in the same enclosure.
The same study also found that ferrets with ocular exposure to the B3.13 genotype H5N1 virus developed severe and transmissible disease, similar to when they were infected by the respiratory route, which the CDC said supports the recommendation for wearing eye protection when exposed to infected or potentially infected animals.
USDA announces funding for poultry avian flu measures
In other H5N1 developments, the USDA today announced up to $100 million in funding for projects to battle avian flu in poultry and reduce the price of eggs.
The three priority areas are novel therapeutics and improved diagnostics, research to better understand how the virus is introduced into poultry flocks and to inform biosecurity mitigation steps, and novel vaccines.
The agency said it consulted with other federal health agencies in setting the funding opportunities. The USDA emphasized that no vaccines are currently authorized and that any decision to move forward with use will involve input from federal agencies, states, veterinarians, farmers, the public health system, and the American public.
More poultry outbreaks in 4 states
Meanwhile, the USDA’s APHIS confirmed more H5N1 detections in poultry flocks from four states, including a layer pullet facility Indiana that has more than 1.3 million birds and a commercial duck breeding farm
Also, the virus hit backyard flocks in Illinois, Kansas, and Montana.
Source : umn.edu