February 26, 20254 min readThe Latest on Bird Flus Hits to Egg Supplies, Rats and CatsAvian influenza continues to fuel egg shortages. Plus, a delayed CDC study on household cats reveals concerning human exposure routesBy Lauren J. Young edited by Tanya LewisBlack rat (Rattus rattus). Claudio Contreras/Nature Picture Library/Alamy Stock PhotoWere regularly rounding up the latest news on avian influenza. Heres what happened recently.Black Rats Test Positive for H5N1Rats have become the latest addition to the menagerie of animals infected with the H5N1 bird flu virus. The U.S. Department of Agricultures Animal and Plant Health Inspection Service reported on February 19 that four black rats from Riverside County, Californiasoutheast of Los Angeles Countyhad tested positive for highly pathogenic avian influenza. As of February 26, the total number of viral detections in mammals reported by the USDA since May 2022 is 514.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.The rats, initially tested in late January, were reportedly associated with two infected poultry farms. The virus had previously been detected in other rodents, such as house and deer mice. Black rats are known to be common in urban areas, which has raised concern of a potential new exposure route for pets and humans. Rodent transmission could also make it harder to contain the spread of bird flu on poultry and dairy farms, where rats and mice may shed the virus in water or animal feed, on equipment and in the environment. Researchers in Japan published a study in July 2024 that found that H5N1 primarily replicates in wild rodents respiratory tract and can be detected in oral swabs. The researchers suggest that the tested rodents, including black rats, brown rats and house mice, could spread the virus to their surroundings via saliva.Infected rodents could also allow the virus to move more readily from farming environments to homes, the Los Angeles Times reported. Scientists and scientific organizations, including the American Veterinary Medical Association, urge farmers and owners of backyard birds and household pets to reduce rodent exposure by fully enclosing the perimeters of animal pens and keeping feed, water and equipment in sealed, out-of-reach places.Delayed Report on Bird Flu in Cats Has Finally Been ReleasedThe Centers for Disease Control and Prevention has posted a Morbidity and Mortality Weekly Report (MMWR) that contains important new developments on household cats infected with bird flu. A February 6 MMWR paper on the effects of wildfire on health initially included information on H5N1 detections in house cats, but those data were quickly taken down, according to the New York Times. The new MMWR report on cats, which was released on February 20, details two cases of infected indoor pet felines in separate households. A female five-year-old shorthair cat had decreased appetite, disorientation and reduced grooming. And a six-month-old male Maine coon experienced facial swelling and loss of appetite. Both showed signs of lethargy and progressive neurological deterioration. Because of the rapid progression of disease in both cases, the female cat was euthanized, and the male cat died within 24 hours of signs of illness.According to the report, neither of the cats had any known direct exposure to farms with H5N1 outbreaks but lived in the respective homes of two Michigan dairy workersboth of whom declined testing. One of the dairy workers, who lives alone, operated on multiple farms transporting raw milk and reported getting splashed on the face, eyes and clothing. The second individual did not work directly with animals or on a farm with a known outbreak. The farm that person worked on was near others that had H5N1 infections, however. The people who lived with the second dairy worker all tested negative for the virus. The report notes that infection sources are still unknown.The holdup of the cat report coincided with an interruption in CDC communications and the removal of information on many government sites to comply with executive orders issued by President Donald Trump. The CDC has not published a press release on bird flu since January 17.Bird flu infections in cats have previously been reported; details of those cases are also limited. Experts hypothesize the animals may have become infected via consumption of raw milk or raw meat from infected wild birds, poultry or rodents.Egg Pricing WoesEgg prices continue to soar as bird flu outbreaks rip through the poultry industry. The USDAs latest weekly egg-market overview report, published on February 21, noted that 36 confirmed outbreaks in nine states have resulted in the loss of 26.8 million egg-laying birds. The pressure of lost poultry is having a direct effect on price: the Bureau of Labor Statistics reported that the average cost of a dozen eggs was $4.95 as of January 2025a record high. Prices may soon rise even higher, however. The USDAs latest egg market overview found cartons delivered to retailers in the week of February 21 averaged $8.47 in New York State, $8.09 in the major Midwestern production region and $9.22 in California.On Monday the U.S.s newly appointed secretary of agriculture Brooke Rollins visited poultry farms in Texas and hosted a roundtable with farmers. At the event, she told ABC News that its possible that prices may continue to rise but that her team will fix it. Rollins added that she and the Trump administration have developed a new plan to control outbreaks in poultry, which she detailed today in an opinion piece in the Wall Street Journal. The current procedure involves slaughtering entire flocks when a case of H5N1 is detected. Rollins says this will still likely be part of the process but that officials are investing in other tactics, including exploring H5N1 vaccines for poultry, reimbursing farmers for lost birds and expanding a program that started under the Biden administration in which the USDA offers farms no-cost biosecurity evaluations.The plan also includes considering egg imports from abroad. Turkey has started to deliver 15,000 metric tons of eggs to replenish U.S. supplies, Reuters reported. Shipments began this month, are expected to continue until July and will cost approximately $26 million to export.