Bird-flu impact may go beyond eggs, birds; experts call for more surveillance as the virus appears able to spread among mammals

Centers for Disease Control and Prevention chart; for a larger version, click on it.

The U.S. is experiencing a record outbreak of bird flu, a virus that is currently deemed a low risk to humans, but has hiked prices of eggs and poultry. The Biden administration is weighing whether to vaccinate poultry against the disease and it appears that the virus can spread among mammals. 

"Egg prices are up 60%, which means we are paying upwards of $5-7 for a dozen eggs. That is if you can find them," reports epidemiologist Katelyn Jetelina in her newsletter titled Your Local Epidemiologist. "Why? A constellation of reasons, but there is one we can’t ignore: the avian flu is hammering poultry farmers." 

The U.S. Department of Agriculture reported in December: "As a result of recurrent outbreaks, U.S. egg inventories were 29 percent lower in the final week of December 2022 than at the beginning of the year. By the end of December, more than 43 million egg-laying hens were lost to the disease itself or to depopulation since the outbreak began in February 2022. . . . The average shelf-egg price was 267 percent higher during the week leading up to Christmas than at the beginning of the year and 210 percent higher than the same time a year earlier." 

USDA adds that egg prices are expected to decrease as flocks are replenished. 

Bird flu spread among minks at a farm in Spain. (Nature photo) 

Another concern is that that virus appears capable of spreading among mammals, including humans.  

"The virus is primarily a threat to birds," reports The New York Times' Emily Anthes, "but infections in mammals increase the odds that the virus could mutate in ways that make it more of a risk to humans, experts say."

Anthes reports that a new variant of the H5N1 virus has "taken an unusually heavy toll on wild birds and repeatedly spilled over into mammals, such as foxes, raccoons and bears, that might feed on infected birds." 

More recently, it has infected farmed minks, which scientists describe as a "new and troubling development," pointing to an outbreak in Spain where the virus appeared to spread from mink to mink and had an unusual mutation that might be a sign of adaptation to mammals, Anthes reports, adding that experts say the mink outbreak is no cause for panic, but highlights the need for more proactive surveillance.  

Michael Osterholm, director of the University of Minnesota’s Center for Infectious Diseases Research and Policy, also told Stat in April 2022 that the presence of bird flu in the U.S. calls for heightened surveillance. Jetelina reports that "from 2003-2021 there have been very few human cases worldwide: 864. But, among these cases, 456 died—a 53% mortality rate." 

Jetelina also notes that the risk of bird flu in humans is "currently very low," citing research from the Centers for Disease Control and Prevention, which tracked the health of more than 5,190 people who have been exposed to infected birds in 2022 and only one human case was reported. The Times reports "fewer than 10 known cases in people since December 2021, and there have been no documented instances of human-to-human transmission, according to the CDC."

Federal scientists are gearing up to test the first vaccines in poultry against the bird flu as a way to counter the growing oubreak, Alexander Tin reports for CBS News. The Biden administration has not yet greenlighted the use of these vaccines. Officials told Tin that one of the concerns about issuing these vaccines is that it could make it harder to export American poultry products. 

"A record 58 million birds — mostly commercially-raised poultry — have died in the outbreak so far, according to figures tallied by the USDA's Animal and Plant Health Inspection Service — either killed by the virus itself or put down in efforts to quash its transmission. Every state has detected the virus spreading among wild birds and 47 have spotted them in poultry," Tin reports.

The virus is spread from an infected bird's nasal secretions, saliva and feces. The USDA says properly prepared and cooked poultry and eggs should pose no risk to consumers. 

"Right now you don’t need to do anything, unless you’re in close contact with birds. A person’s level of risk is dependent on duration and intensity of exposure. In other words, a person with one chicken in their backyard is at much lower risk than someone at a poultry farm," Jetelina writes. 

She adds, "Those around wild birds, such as at parks, lakes, rivers, or other waterways, need to exercise caution, including wearing PPE, washing hands, and changing clothes. If you have backyard poultry, wear a mask and wash your hands. Also, monitor the health of your flock, especially if they come in contact with other wild birds."