After a Panhandle man tested positive for a “highly pathogenic avian influenza”—a.k.a. bird flu—last week, it’s understandable for Texans to foster concerns about the potential onset of another pandemic. But federal and state health authorities, as well as infectious disease doctors, have emphasized that the risk remains low.
Primarily, that’s because the virus, known as H5N1, which has been circulating worldwide since at least 1996, hasn’t yet demonstrated the ability to jump from one person to another. The Texan who contracted the latest strain of the pathogen worked with a population of dairy cattle that were known to have recently been infected. He is only the second person confirmed to have bird flu in the United States, following a case two years ago in Colorado.
“There’s no immediate cause for alarm or concern to Texans. This is not a brand new virus like COVID-19,” says Larry Schlesinger, an infectious disease physician and president and CEO of the Texas Biomedical Research Institute, in San Antonio. “In recent years, the human cases have been mild and strictly related to occupational exposures—unprotected workers who are exposed primarily to poultry.”
Nevertheless, H5N1 continues to evolve. If two subtypes of this flu infect the same animal at once—as often happens in birds, the natural host of the influenza virus—their gene segments can mix and match into new strains. The accumulating mutations typically result in an increasing ability to infect a greater diversity of hosts. So infectious disease researchers are preparing for the possibility of eventual human-to-human transmission of the bug.
“The good news is that this process most typically leads to accumulated mutations that make the virus less disease-causing, or virulent,” Schlesinger says. “COVID-19 was, in fact, a rare and unusual case where a mutation created a completely different infection-to-disease progression in humans than had been seen before.”
Texas Biomed numbers among only a few research centers in the country with federal approval to study H5N1. The institute, in conjunction with the CDC, is testing whether vaccines developed for earlier versions of bird flu offer protection against the latest strains, as well as attempting to develop a new vaccine.
“We’re not really prepared well enough for future events that might occur,” Schlesinger says. “There needs to be much more work going on to develop more diagnostics, therapies, and vaccines to handle what might be the next big problem in infectious diseases.”
Saad Omer, a Dallas epidemiologist, agrees that public health authorities must remain vigilant in monitoring cases and any changes in transmission patterns. The CDC uses an Influenza Risk Assessment Tool to assess the likelihood that a particular virus could spark the next pandemic. The most recent H5N1 viruses the CDC assessed with this tool were linked to an October 2022 outbreak among minks and a March 2022 infection in an American wigeon duck—the first confirmed case of avian influenza in a wild bird in the U.S. since 2016. Both viruses were deemed “moderate” risks. The CDC will likewise analyze this latest strain of the virus but has not yet published any data.
After sequencing the genome from the virus that infected the Texan and comparing it to other H5N1 strains, the CDC reported Friday that the virus in the person is “nearly identical” to those found in the cattle and birds on the dairy property, with “no changes associated with resistance to antiviral medications.” The virus is also similar to two viruses the CDC had already stored for the purpose of making a future vaccine, if the need arises.
The CDC must rely on data gathered by local and state authorities to stay prepared. Omer says it’s “hard to put a specific number on the probability” that bird flu will become a human-borne disease, and such uncertainty is why close surveillance of the virus and its mutations is critical.
Therein lies the rub. Schlesinger worries about the “roller coaster of financial support for public health infrastructure related to infectious diseases.” Money often only reliably flows into such efforts when threats appear immediate. Yet viruses currently deemed of low risk to humans—H5N1 or any of several other types of influenza A—could become the next big problem, even if not right away.
H5N1 is widespread in wild birds and has been causing sporadic outbreaks in poultry flocks—both on commercial farms and in backyard chicken coops—for years. Infected birds shed the virus through their saliva, mucus, or feces. Cases among mammals remain rare enough that the USDA tracks and maps individual cases.
The Texas Animal Health Commission began monitoring a syndrome in dairy cattle in early March, according to an agency spokesperson. Dead wild birds and dead cats had also been found on the dairy property, and testing eventually revealed that all three species carried H5N1, a first for U.S. dairy cattle. The virus is considered highly pathogenic because of its high death rate among infected poultry.
Symptoms for the infected Panhandle cattle appear mild, and the milk from those cows is not being used. The spokesperson for TAHC told Texas Monthly that protocols are in place to ensure that milk and meat supplies are safe to consume (no beef cattle are known to have been infected). Yet in a subsequent incident, the largest U.S. fresh egg producer has halted production at a Texas plant, also in the Panhandle, after bird flu was detected in the plant’s flock. No eggs have been recalled so far, and it’s unclear whether this outbreak is linked to the infected dairy cattle.
Human cases of avian flu—resulting in fever, cough, sore throat, runny nose, headache, fatigue, eye redness, nausea, vomiting, or diarrhea—have been severe enough to cause death, but in recent years they have typically been mild and treatable with antiviral medications.
The infected Texan experienced only red and irritated eyes. The only reason his infection was detected was because of the routine testing instituted for all of those working with the infected cattle, according to the Texas Department of State Health Services. A spokesperson for the agency added that eye doctors treating conjunctivitis should ask whether their patients have had recent contact with livestock or birds.
While most Texans aren’t at risk, some may want to exercise extra caution, such as those with backyard chickens or those who interact with livestock, including youth who raise animals for shows, for example. It’s been rare even for people working with wild birds, such as wildlife rehabilitators, to get infected, a DSHS spokesperson says, but those who do work with wild birds need to protect themselves from the birds’ secretions, typically with gloves, masks, and goggles.
TAHC officials haven’t determined how H5N1 was transmitted to the cattle, though contact with wild birds is a possibility. The virus having found a new type of host, however, underscores the importance of continued surveillance and public health funding, Schlesinger says.
“The major key to infectious disease threats is to have a head start,” he says, “to have the resources and the know-how to create these countermeasures ahead of any potential problem.”
