At least one person in Texas has been diagnosed with bird flu after coming into contact with a cow suspected of having the disease. state officials said on Monday.
The news casts worrying light on the outbreak, which has affected millions of birds and marine mammals around the world and, most recently, dairy cows in the United States.
Federal officials say so far there is no indication that the virus has evolved to spread more easily from person to person.
The patient’s main symptom was conjunctivitis; the person was being treated with antiviral medications and is currently recovering, according to the Centers for Disease Control and Prevention.
Ministry of Agriculture announced The first cases were in Dairy herds in Texas and Kansas last week, and A few days later, in another herd in Michigan. Preliminary testing suggests that dairy cows in New Mexico and Idaho may also be infected.
The virus has been identified as the same version of influenza subtype H5N1 that circulates in North American birds.
The CDC said Monday it is working with state health departments to monitor other people who may have been exposed to infected birds and animals.
This is only the second case of human infection with H5N1 avian influenza in the United States; this The first time will be in 2022. Experts say the risk to the public remains low. But testing and analysis are still ongoing, and there are many unanswered questions.
“The situation is evolving rapidly,” the USDA said in a statement last week.
Here’s what you need to know:
What is avian influenza?
Avian influenza, or avian influenza, is a group of influenza viruses that are primarily adapted to birds. The particular virus in these new cases is called H5N1, which was first discovered in geese in China in 1996 and in people in Hong Kong in 1997.
In 2020, a new highly pathogenic H5N1 virus emerged in Europe and spread rapidly around the world.In the United States, it has affected More than 82 million farmed birdsthe worst avian influenza epidemic in U.S. history.
Sporadic spread of the virus since it was first discovered Cases have also been detected in people from other countries. But the vast majority are caused by long-term direct contact with birds.
Experts say H5N1 does not appear to have adapted to spread effectively among people.
How do cows become infected with avian influenza?
Dairy cows are not considered a high-risk species.
“The fact that they’re so susceptible to infection — the virus can replicate and it can make them sick — is 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 on some of the farms, and laboratory tests confirmed that some cows were infected with avian influenza.
The virus may enter cattle in a number of ways. Several experts said the likely route is infected wild birds shedding the virus through feces, saliva and other secretions that contaminate 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 brought the virus to dairy farms.
How are cows affected?
Although the virus is often fatal to birds, it appears to cause relatively mild disease in dairy cows.
“It’s not killing the animals, and they seem to be recovering,” said Dr. Joe Armstrong, a veterinarian and cattle production specialist at the University of Minnesota Extension.Last week, the U.S. Department of Agriculture said No plan “Reduce” or kill affected herds is standard procedure when poultry flocks become infected with the virus.
The disease mainly affects older cows, where symptoms include loss of appetite, low-grade fever and a significant drop in milk production. Milk from cows is often “thick and discolored” According to Texas officials. The virus has also been found in unpasteurized milk samples collected from sick cows.
Experts warn that it is not yet clear whether the avian flu virus is the sole cause of all the symptoms and illnesses reported.
How common is this problem?
It’s not clear yet. As of Friday, the USDA’s National Veterinary Services Laboratory had confirmed avian influenza infections in two herds in Texas, two in Kansas and one in Michigan.
Preliminary testing suggests other cattle herds in Texas, New Mexico and Idaho may also be infected with the virus, but those findings have not yet been confirmed by state laboratories. So far, the virus has only been found in dairy cows and not yet in beef cattle.
But experts say there may be other infected herds that go undetected because cows are not regularly tested for bird flu and the disease is relatively mild.
The movement of cattle between states could spread the virus to new locations. Affected dairy farms in Michigan recently imported cows from an infected herd in Texas. When the cows were transported, they showed no symptoms.Idaho farms also recently imported dairy cows from affected Idaho officials said.
How does it spread?
This is a critical and still unanswered question. It is possible for infected cows to become infected independently, especially if shared food or water sources are contaminated.
However, a more worrying possibility is that the virus is spreading between cows. On Friday, the USDA noted that “transmission among cattle cannot be ruled out.”
Several scientists said they would be surprised if there wasn’t some degree of transmission from cattle to cattle. “How else could it have moved so fast?” said Dr. Gregory Gray, an infectious disease epidemiologist at the University of Texas Medical Branch.
If the virus spreads easily between cows, it could lead to larger, more sustained outbreaks. It would also give the virus more opportunities to adapt to new mammalian hosts, increasing the risk that it will mutate and become more dangerous to humans.
How do officials know if bird flu is adaptable to human-to-human transmission?
Analyzing viral genetic sequences from infected birds, cattle and humans could reveal whether H5N1 has acquired mutations that help it spread through humans.
Scientists have been closely tracking infections in birds and marine mammals and are now tracking infections in dairy cows. So far, the virus does not appear to have the ability to spread effectively from person to person.
In 2012, scientists demonstrated that H5N1 could spread through air Experiments were conducted on ferrets, a popular model for studying human-to-human transmission of respiratory viruses, after acquiring five mutations.
A bird flu sample isolated from a Chilean man last year had two mutations that suggested adaptations to infecting mammals. But experts say these mutations have appeared before without the virus evolving further and spreading from person to person.
