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At least one person in Texas has contracted bird flu after coming into contact with suspected infected dairy cows. Government officials said. on Monday.

The announcement adds a level of concern to an outbreak that has killed 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 ways that allow it to spread easily between people, federal officials said.

Texas State Health Services spokeswoman Lara M. Anton said the patient had worked directly with sick dairy cows. “We tested about a dozen symptomatic people who worked at the dairy and only one person tested positive for the virus,” he said in an email.

The primary symptom of the patient is conjunctivitis; The man is being treated with antiviral drugs and is recovering, according to the Centers for Disease Control and Prevention.

Department of Agriculture announced In the first cases Dairy herds in Texas and Kansas last week, and After a few days, in more herds in Michigan. Preliminary testing shows that cows in New Mexico and Idaho may also be infected.

The virus was identified as a similar version of the influenza subtype H5N1 circulating in North American birds.

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 not to be exposed to sick or dead birds and animals, as well as raw milk, feces or other potentially contaminated materials.

This is the second case of H5N1 bird flu in humans in the United States; of It was first in 2022.. Experts say the risk to the public is low. But testing and analysis is ongoing, and there are many unanswered questions.

“This is a rapidly evolving situation,” the USDA said in an announcement last week.

Here’s what you need to know:

Bird flu, or avian influenza, is a group of flu viruses that are primarily suitable for birds. The specific virus in these new cases was identified as H5N1 in geese in China in 1996, and in humans in Hong Kong in 1997.

In the year By 2020, a new, highly pathogenic form of HIV in Europe In the United States, it has had an impact More than 82 million breeding birdsThe worst bird flu outbreak in US history.

Since the virus was first discovered, rarely Cases have been found in humans in other countries. But most of them are extended and in direct contact with birds.

H5N1 does not yet appear to have adapted to spread efficiently between humans, experts say.

Cows were not considered an endangered species.

“The fact that they’re susceptible to the disease — that the virus can multiply, that they can get sick — that’s something I didn’t anticipate,” said Richard Webby, an influenza virologist at St. Jude Children’s Research Hospital.

But this year, reports of sick cows began to appear in Texas and New Mexico. Dead birds were also found in these farms and laboratory tests confirmed that some cows were infected with bird flu.

There are several ways in which the virus can enter cattle. Many experts say that the virus is shed in feces, saliva and other fluids by wild birds that contaminate the cows’ food or water.

But other free-ranging animals known to be susceptible to the virus, such as cats and raccoons, could have brought the virus to dairy farms.

While the virus is often fatal in birds, it appears to be causing a relatively mild illness in cows.

“It’s not killing the animals, and they seem to be recovering,” said Dr. Joe Armstrong, a veterinarian and livestock specialist at the University of Minnesota Extension. Last week, the USDA said There were no plans To “de-populate” or cull affected flocks, which is a standard practice in poultry flocks infected with the virus.

The disease mainly affects older cows, and symptoms include loss of appetite, low-grade fever and significantly reduced milk production. The milk produced by the cows is usually “thick and colored”. According to Texas officials. The virus has also been found in raw milk samples collected from sick cows.

Experts warn that the bird flu virus is not the sole cause of the reported symptoms and illnesses.

It is not clear. As of last Friday, the USDA’s National Veterinary Services Laboratory has confirmed cases of bird flu in two flocks in Texas, two flocks in Kansas and one flock in Michigan.

Initial testing suggests additional herds in Texas, New Mexico and Idaho may have the virus, but those findings have not yet been confirmed by the national lab. So far, the virus has only been found in dairy cows and not in beef cattle.

But because cows are not routinely tested for bird flu and the illness was relatively mild, experts say there may have been other infected herds that escaped the disease.

And the movement of cattle between regions can transport the virus to new areas. The affected dairy in Michigan had recently imported cows from an infected herd in Texas. When the cows were transported, the animals did not show any signs. The farm in Idaho recently imported cows from the affected state of Idaho Officials said..

That is a key and still unanswered question. It is possible that the infected cows are picking up the virus individually, especially if shared food or water sources are contaminated.

What is more worrying is that the virus is being spread from cow to cow. On Friday, the USDA said “transitions between cattle cannot be ruled out.”

Many scientists have said that they would be surprised if there is some level of transmission from cow to cow. “How else can he move so fast?” Dr. Gregory Gray, an infectious disease epidemiologist at the University of Texas Medical Branch, said.

If the virus can easily spread among cows, that could lead to large and ongoing outbreaks. It also gives the virus more opportunities to adapt to new mammals, increasing the risk of acquiring mutations that make it more dangerous to humans.

It shows that the genetic sequence of the virus from infected birds, cows and humans has been analyzed to determine whether H5N1 has acquired a mutation that allows it to spread between humans.

Scientists are closely monitoring infections in birds and marine mammals, and now cows. So far, the virus does not seem to have the ability to spread efficiently between humans.

In the year In 2012, scientists showed that H5N1 It is spread by air Among ferrets – a popular model for studying the spread of respiratory viruses between humans – after finding five mutations.

A bird flu sample isolated from a Chilean man last year had two mutations that indicate an adaptation to infecting mammals. But those mutations have been seen before without the virus spreading between humans, experts said.

Federal officials stress that commercial flavored milk is safe to drink. Dairy producers are required to keep milk from sick animals out of the human food supply, and milk sold in government lines must be softened, a process that heats the milk to kill pathogens. Pasteurization “is proven to permanently kill bacteria and viruses in milk, such as influenza,” according to the Food and Drug Administration. New online guide on milk safety.

Veterinary public health expert and independent consultant Dr Gail Hansen agreed that the risk of contamination from pasteurized milk is “very low”. “I don’t want people to stop drinking milk because of this,” she added.

But the possibility can’t be completely ruled out, she said, adding that federal officials were worried about being “overconfident in the face of so many unknowns.” If cows are getting the virus into their milk before they show symptoms, that milk can enter the commercial milk supply, she said. And different pathogens may require different pasteurization temperatures and durations; The specific conditions required to activate this particular virus are unclear, Dr. Hanson said.

The risk of contracting the virus from eating unpasteurized or raw dairy products is not known, the FDA said. Raw milk is known to cause a variety of potential health risks beyond bird flu.