April 12, 2024

Person infected with bird flu in Texas after contact with livestock

At least one person in Texas has been diagnosed with bird flu after contact with suspected infected dairy cows, state officials said Monday.

The announcement adds a worrying dimension to an outbreak that has affected millions of birds and marine mammals worldwide and, most recently, cows in the United States.

So far, there are no signs that the virus has evolved in a way that would make it easier to spread among people, federal officials say.

The patient’s main symptom was conjunctivitis; the individual is treated with an antiviral drug and recovers, according to the Centers for Disease Control and Prevention.

The Department of Agriculture announced the first cases last week in dairy herds in Texas and Kansas, and a few days later in an additional herd in Michigan. Preliminary testing suggests cows in New Mexico and Idaho may also be infected.

The virus has been identified as the same version of H5N1, a flu subtype, that is circulating among North American birds.

The CDC is working with state health departments to monitor others who may have come into contact with infected birds and animals, the agency said Monday.

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

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

Here’s what you need to know:

Bird flu, or bird flu, is a group of influenza viruses that are mainly adapted to birds. The specific virus in these new cases, called H5N1, was first identified in 1996 in geese in China, and in 1997 in humans in Hong Kong.

In 2020, a new, highly pathogenic form of H5N1 emerged in Europe and quickly spread throughout the world. More than 82 million farmed birds have been affected in the United States, the worst outbreak of bird flu in US history.

Cases have also been sporadic since the virus was first identified cases in people in other countries. According to the World Health Organization, in 2023 there were 248 cases of people infected with the H5N1 virus and 139 deaths. But the vast majority resulted from prolonged, direct contact with birds.

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

Cows were not considered a high-risk species.

“The fact that they are susceptible — the virus can replicate, can make them sick — I wouldn’t have predicted that,” said Richard Webby, an influenza virologist at St. Jude Children’s Research Hospital.

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

There are several ways in which the virus can enter livestock. The most likely route, according to several experts, is that infected wild birds, which shed the virus through their feces and oral secretions, 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 onto dairy farms.

Although the virus is often fatal in birds, it appears to cause relatively mild illness in cows.

“It doesn’t kill animals, and they seem to recover,” says Dr. Joe Armstrong, a veterinarian and livestock production expert at the University of Minnesota Extension. Last week, the USDA said there were no plans to “depopulate” or kill affected flocks, which is standard procedure when poultry flocks are 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 the cows produce is often “thick and discolored,” Texas officials said. The virus has also been found in unpasteurized milk samples from sick cows.

It is not yet clear whether the bird flu virus is the sole cause of all reported symptoms and illnesses, experts warned.

It is unclear. As of Friday, the USDA’s National Veterinary Services Laboratory had confirmed bird flu infections in two herds in Texas, two herds in Kansas and one herd in Michigan. Initial testing has shown that additional herds in Texas, New Mexico and Idaho may also be infected with the virus, but these findings have not yet been confirmed by the national laboratory. So far it has only been found in dairy cows and not in beef cattle.

But because cows are not routinely tested for bird flu and the disease has been relatively mild, there may be other infected herds that have escaped detection, experts said.

And the movement of livestock between states could transport the virus to new locations. The affected Michigan dairy farm had recently imported cows from one of the infected herds in Texas. At the time the cows were transported, the animals showed no complaints. The Idaho farm had also recently imported cows from an affected state, Idaho officials said.

That is an important, and still unanswered, question. It is possible that the infected cows could all contract the virus independently, especially if shared food or water sources are contaminated.

A more worrying possibility, however, is that the virus is spreading from cow to cow. On Friday, the USDA noted that “transmission between livestock cannot be ruled out.”

Several scientists said they would be surprised if some degree of cow-to-cow transmission did not occur. “How else could it happen so quickly?” said dr. Gregory Gray, an infectious disease epidemiologist at the University of Texas Medical Branch.

If it turns out that the virus spreads easily between cows, it could lead to larger and longer-lasting outbreaks. It would also give the virus more opportunities to adapt to its new mammalian hosts, increasing the risk of it acquiring mutations that make it more dangerous to humans.

Analyzing the genetic sequence of the virus from infected birds, cows and humans can reveal whether H5N1 has acquired mutations that cause the virus to spread among humans.

Scientists have been closely monitoring infections in birds and marine mammals, and now in cows. So far, the virus appears to have failed to spread efficiently between people.

In 2012, scientists showed that H5N1 could spread through the air between ferrets — a popular model for studying the transmission of respiratory viruses among humans — after acquiring five mutations.

A sample of bird flu isolated from a Chilean man last year showed two mutations that indicate an adaptation to infecting mammals. But those mutations have been observed before without the virus evolving and spreading between people, experts said.

Leave a Reply

Your email address will not be published. Required fields are marked *