After a Texas dairy worker was infected last month with bird flu — the first known case of a person catching the virus from a cow — should North Texans be concerned?
The short answer is no, said Dr. Varun Shetty, chief state epidemiologist for the Texas Department of State Health Services, and Dr. Julie Trivedi, an associate professor in the Department of Internal Medicine at UT Southwestern Medical Center.
Here’s what you need to know.
What is bird flu?
Human cases of bird flu are exceedingly rare. Before the one in Texas, the first and previous case of H5N1 in the United States happened in Colorado in 2022. Both people had mild symptoms and recovered. But of the 26 human cases of H5N1 reported around the world since January 2022, seven resulted in death.
Bird flu is part of a family of influenza viruses, which come in four types (A, B, C, and D) that typically cause respiratory infections. Bird flu is a type A influenza virus — one of the most common types responsible for seasonal epidemics during the colder months — and comes in two forms: low pathogenic avian influenza (LPAI) causing mild or no illness at all, as seen in chickens; and a highly pathogenic avian influenza (HPAI), which is highly contagious and deadly to poultry. The variant at the heart of the current outbreak — H5N1 — particularly affects wild birds, is highly pathogenic, and responsible for previous outbreaks among domestic birds.
The letters H and N refer to proteins on the surface of the virus — called hemagglutinin and neuraminidase — that mutate constantly, resulting in new strains and periodic outbreaks and epidemics.
In the United States, avian influenzas have been known to infect and kill domestic poultry. A poultry facility in Farwell was required to “depopulate” 1.6 million laying hens and 337,000 pullets in April after reporting a positive test for bird flu.
H5N1 was first detected in domestic waterfowl in southern China in 1996 and spread to migratory wild birds around 2005. It’s mostly remained among wild birds, but in recent years there have been reports of cases and outbreaks among other species. These include sea lions, grizzly bears, and more recently, dairy cows. The spread has raised concerns among scientists and public health institutions about the virus adapting to infect other mammals, including humans.
Can humans can get infected?
The confirmed human case of bird flu in Texas may cause concern, but Shetty and Trivedi said the risk of bird flu spreading among people is very low. Research by the Centers for Disease Control and Prevention found that the virus does not appear to be mutating in a way that would make it more likely to infect humans or resist antiviral medications, Shetty said.
Because bird flu spreads through the air or through contact with contaminated surfaces, Shetty recommends Texans who work or interact with farm animals wear protective equipment. Demetre Daskalakis, director of the CDC’s National Center for Immunization and Respiratory Diseases, said in a press conference last week that the agency would provide farm workers guidance on precautions and proper protective equipment, including a graphic in both English and Spanish.
Some scientists have voiced concern that human cases of bird flu may be going unreported. Shetty said the Texas Department of State Health Services and the CDC are monitoring for any unusual influenza activity; so far, there hasn’t been an increase in cases or in the number of people coming into clinics or emergency rooms with flu-like symptoms in Texas, he said. Nationally, more than 100 farm workers who were exposed to infected animals were monitored for 10 days for any sign of infection and then tested again, Daskalakis said.
Trivedi of UT Southwestern said there will be certain populations, such as farm or livestock workers, who will be at a higher risk of exposure and potentially getting infected with bird flu. “I don’t think this is something that, let’s say the general population in the city of Dallas, needs to go and get themselves tested for,” Trivedi said. However, she recommends that if someone is experiencing flu-like symptoms or eye redness (also known as conjunctivitis), they should consult a health care provider.
There is no specific diagnostic test for the bird flu. If a nasal or throat swab comes back positive for influenza A, hospitals or health departments often do further genetic testing, if indicated, to determine the exact variant, whether H5N1 or another, said Trivedi.
The seasonal flu vaccine won’t prevent infection, but it can reduce your chances of getting both the bird and seasonal flu at the same time, according to the CDC.
How did cattle get infected?
During last week’s press conference, health officials said a spillover event — when a virus hops from one species to another — occurred in a number of Texas cattle herds. This highly infectious variant of H5N1 spread as those infected cows were transported to other states; one dairy operation in Ohio received cows from an infected Texas herd, according to the American Veterinary Medical Association.
Thirty-six herds with confirmed infections are spread out across nine states, including Texas, the USDA reported. Farmers with affected herds are reporting that 10% of their cattle are showing bird-flu symptoms, but the infected cows are recovering within about two weeks with “little or no associated mortality,” said Rosemary Sifford, the USDA’s chief veterinary officer, during the press conference.
To prevent the virus from spreading across the nation, the Department of Agriculture issued mandatory guidelines last week for farmers transporting dairy cows across state lines. Lactating cows must test negative for influenza A viruses before transport, and any animals that test positive must be reported. But these new federal guidelines only require testing 30 animals in a group, and there is no clear guidance on which animals a farmer should include or select, several publications reported.
Are dairy and meat products safe for human consumption?
Viral fragments of bird flu have been detected in cow’s milk from infected animals and commercial sources. Because of pasteurization, which kills H5N1, preliminary tests suggest dairy milk is safe to drink. But raw milk, which is available for sale in Texas by licensed dairy retailers, may be unsafe.
“We do not recommend people consume raw milk products,” Shetty said. “If you’re consuming products that have a potentially high load of virus in it, it’s possible that it could make you sick.”
The Texas Department of State Health Services requires licensed raw-for-retail dairies to have their milk tested, at least on a quarterly basis, according to the agency’s website. In an email to The Dallas Morning News, spokesperson Lara Anton said the agency’s requirements for raw milk sellers remain the same.
Ground beef has tested negative for bird flu based on 30 samples collected from retail outlets in the states with infected dairy cows, USDA officials said Wednesday. As long as meat is handled and cooked properly, it’s considered safe to eat.
Miriam Fauzia is a science reporting fellow at The Dallas Morning News. Her fellowship is supported by the University of Texas at Dallas. The News makes all editorial decisions.
