At least one person in Texas has been diagnosed with bird flu after coming into contact with suspected infected dairy cows. state officials said Monday.
This announcement adds a worrying dimension to an epidemic that has affected millions of birds and marine mammals around the world and, more recently, cows in the United States.
So far, there are no signs that the virus has evolved in a way that would help it spread more easily among people, federal officials said.
The patient worked directly with sick dairy cows, said Lara M. Anton, a representative with the Texas Department of State Health Services. “We tested a dozen symptomatic people working in dairies, and only one person tested positive” for the virus, she said in an email.
The patient’s main symptom was conjunctivitis; the individual is treated with an antiviral medication and recovers, according to the Centers for Disease Control and Prevention.
The Ministry of Agriculture announced the first cases in dairy herds in Texas and Kansas last week, and a few days later, in an additional herd in Michigan. Preliminary tests suggest cows in New Mexico and Idaho may also be infected.
The virus was identified as the same version of H5N1, a subtype of influenza, that is circulating in birds in North America.
The CDC is working with state health departments to monitor other people who may have come into contact with infected birds and animals, the agency said Monday. He also urged people to avoid exposure to sick or dead birds and animals, as well as raw milk, feces or other potentially contaminated materials.
This is only the second case of H5N1 bird flu in people in the United States; THE the first time was in 2022. The risk to the general public remains low, experts say. But tests and analyzes are ongoing and many questions remain unanswered.
“This is a rapidly evolving situation,” the USDA said in its statement last week.
Here’s what you need to know:
What is bird flu?
Avian influenza, or bird flu, is a group of influenza viruses primarily adapted to birds. The particular virus involved in these new cases, called H5N1, was first identified in 1996 in geese in China and in people in Hong Kong in 1997.
In 2020, a new, highly pathogenic form of H5N1 appeared in Europe and spread rapidly around the world. In the United States, this affected more than 82 million breeding birdsthe worst bird flu outbreak in U.S. history.
Since the virus was first identified, cases have been found in people in other countries. But the vast majority of them result from direct and prolonged contact with birds.
Experts say H5N1 does not yet appear to have adapted to spread effectively among humans.
How did cows get bird flu?
Cows are not considered a high risk species.
“The fact that they are susceptible — the virus can replicate, can make them sick — that’s something I wouldn’t have predicted,” said Richard Webby, an influenza virologist at the Research Hospital for St. Jude children.
But this year, reports of sick cows began emerging in Texas and New Mexico. Dead birds were also found on some of these farms, and laboratory tests confirmed that some cows were infected with bird flu.
The virus could have spread in cattle in various ways. The likely pathway, several experts say, is that infected wild birds, which shed the virus in their droppings, saliva and other secretions, contaminated the cows’ food or water.
But other free-ranging animals known to be susceptible to the virus, such as cats and raccoons, may also have introduced the virus to dairy farms.
How were the cows affected?
Although the virus is often fatal in birds, it appears to cause relatively mild illness in cows.
“It’s not killing any animals, and they seem to be recovering,” said Dr. Joe Armstrong, a veterinarian and animal production expert at the University of Minnesota Extension. Last week, the USDA said that there was no plan to “depopulate” or kill affected flocks, which is standard procedure when poultry flocks become infected with the virus.
The disease mainly affects older cows, which have developed symptoms such as loss of appetite, mild fever and a significant drop in milk production. The milk produced by cows is often “thick and discolored.” according to Texas officials. The virus has also been detected in samples of unpasteurized milk taken from sick cows.
It is not yet clear whether the bird flu virus is the sole cause of all the reported symptoms and illnesses, experts warn.
How big is the problem?
It’s unclear. As of Friday, the USDA National Veterinary Services Laboratory had confirmed avian flu infections in two flocks in Texas, two flocks in Kansas and one flock in Michigan.
Initial testing suggested other herds in Texas, New Mexico and Idaho may also have the virus, but those results have not yet been confirmed by the national lab. So far, the virus has only been detected in dairy cows and not in beef cattle.
But because cows are not routinely tested for bird flu and the disease is relatively mild, there could be other infected herds that have escaped detection, experts said.
And interstate livestock movements could carry the virus to new locations. The affected Michigan dairy had recently imported cows from an infected Texas herd. When the cows were transported, the animals showed no symptoms. The Idaho farm had also recently imported cows from an affected state, Idaho. officials said.
How is it spread?
This is a key question, and still unanswered. It is possible for infected cows to contract the virus independently, especially if shared feed or water sources have been contaminated.
A more worrying possibility, however, is that the virus is spreading from cow to cow. On Friday, the USDA noted that “transmission between cattle cannot be ruled out.”
Several scientists said they would be surprised if there wasn’t some degree of cow-to-cow transmission. “Otherwise, how could it go so quickly? said Dr. Gregory Gray, an infectious disease epidemiologist at the University of Texas Medical Branch.
If the virus can spread easily between cows, it could lead to larger, longer-lasting outbreaks. It would also give the virus more opportunity to adapt to its new mammalian hosts, increasing the risk that it will acquire mutations that make it more dangerous to humans.
How will authorities know if bird flu adapts to spread among humans?
Analyzing the genetic sequence of the virus from infected birds, cows and humans can reveal whether H5N1 has acquired mutations that contribute to its spread among humans.
Scientists are closely monitoring infections in birds and marine mammals and, now, in cows. So far, the virus does not appear to have the ability to spread effectively among humans.
In 2012, scientists showed that H5N1 was capable of spread through the air in ferrets – a popular model for studying the transmission of respiratory viruses between humans – after acquiring five mutations.
A bird flu sample isolated from a Chilean man last year had two mutations that indicate adaptation to infectious mammals. But these mutations have already been observed without the virus evolving further to spread among humans, experts said.
Is it safe to consume dairy products?
Federal officials stressed that commercially processed milk remains safe to drink. Dairies are required to keep milk from sick animals out of the human food supply, and milk sold across state lines must be pasteurized, a process in which milk is heated to kill potential pathogens. Pasteurization “has continually been shown to inactivate bacteria and viruses, such as influenza, in milk,” the Food and Drug Administration said in a statement. new online guide to milk safety.
Dr Gail Hansen, a veterinary public health expert and independent consultant, agreed that the risk of becoming infected from pasteurized milk was probably “very low”. She added: “I wouldn’t want people to stop drinking milk because of this. »
But that possibility can’t be ruled out entirely, she said, expressing some concern that federal officials were “overconfident in the face of so many unknowns.” If cows shed viruses in their milk before showing signs of illness, that milk could potentially end up in the commercial milk supply, she said. And different pathogens may require different pasteurization temperatures and durations; The specific conditions required to inactivate this particular virus remain unclear, Dr. Hansen said.
The risk of becoming infected with the virus from consuming unpasteurized or raw dairy products remains unknown, the FDA said. Raw milk is known to pose various potential risks of illnesses other than avian flu.
