Today
In early April, a Texas dairy worker tested positive for bird flu, amid a multistate outbreak of the virus among cows. The bird flu virus too has been detected in unpasteurized milkbut authorities assure that the current risk to the public is low.
It is the first time that this strain of bird flu—called highly pathogenic avian influenza A (H5N1)—has been detected in cattle, and the first documented transmission from a cow to a human, according to the Centers for Disease Control and Prevention. Diseases of the United States (CDC).
The infected person in Texas was only the second human case of bird flu reported in the United States.
Although there is no evidence of human-to-human transmission of the highly pathogenic H5N1 strain, health authorities are on high alert.
At a recent press conference, a leading World Health Organization (WHO) expert called the risk of bird flu spreading to humans a “huge concern.” Dr. Jeremy Farrar, WHO chief scientist, warned in a press conference on April 18 that bird flu viruses are increasingly infecting mammals.
“The big concern (…) is that the virus evolves and develops the capacity to infect humans and, what is more serious, to move on to human-to-human transmission,” Farrar said.
How concerning is the strain?
The current bird flu outbreak has affected cows at more than a dozen dairy factories across the country. Although the risk to humans has been considered low, health authorities called for increased surveillance of infected animals and people exposed to them.
Although thinking about bird flu may sound alarming and may bring back fears of the COVID-19 pandemic, flu among birds is not new.
“The current strain of bird flu that we are concerned about, H5N1, has been circulating in the world for quite some time,” Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, told .com.
The H5N1 virus is widespread among wild birds and is causing an outbreak among poultry in the United States, according to the CDC.
What is bird flu?
Avian influenza is a disease caused by infection with the avian influenza type A virus. Avian influenza type A viruses occur naturally among wild waterfowl, such as geese, ducks and swans, Schaffner explained. , but they can also circulate among domestic poultry.
“Avian influenza viruses are occasionally introduced into other mammal species (such as pigs). “We've all heard of swine flu,” Schaffner said. According to the CDC, avian influenza A viruses can also infect horses, bats, and dogs, and are rarely transmitted to humans.
“More recently, we have seen an increase in infections in livestock,” Dr. Hilary M. Babcock, an infectious disease specialist at Washington University in St. Louis and BJC Healthcare, told .com.
It is the first time that the H5N1 strain of bird flu, highly pathogenic and causing serious and often fatal diseases in birds, has been detected in cows. “It's pretty unusual,” Schaffner said. However, this strain has not seemed to make cows very sick, she explained.
Which states have detected the strain?
Highly pathogenic avian influenza viruses (including the H5N1 strain currently spreading) were detected in the United States in wild waterfowl, commercial poultry, and flocks of backyard birds beginning in January 2022, the researchers said. CDC.
In total, 48 states have reported cases of the highly pathogenic H5N1 virus.
The current H5N1 outbreak affecting cows has so far spread to eight states, according to the United States Department of Agriculture (USDA). Until April 11, cases had been reported in dairy herds of:
- Texas
- Kansas
- Michigan
- New Mexico
- Idaho
- Ohio
- North Carolina
- South Dakota
Currently, only one human being in Texas is known to have contracted the H5N1 virus in this outbreak, experts said.
There have only been two cases of H5N1 in humans in the country: the first was detected in Colorado during 2022 in a person who was in direct contact with infected poultry.
As surveillance on the H5N1 strain increases, experts believe the number of cases among cows will increase. “Now we look harder and find more cases (among cattle) that even 10 years ago would have gone unnoticed,” Schaffner added.
According to experts, the risk to the general American population is low. For people exposed due to their work, the risk has been considered “low to moderate,” a WHO statement explained.
How is bird flu transmitted to humans?
“Occasionally, a bird flu virus can be transmitted to a human, but it is rare,” Schaffner added. According to the CDC, bird flu viruses can be transmitted from infected birds to humans in several ways:
- Directly from an infected bird.
- From environments contaminated with the virus.
- Through an intermediate host, such as an animal.
Infected birds can spread the virus in their saliva, nasal secretions, mucus, and feces. People can become infected when a large enough amount of the virus enters the mouth, nose, eyes or is inhaled, Schaffner said.
Transmission to humans usually occurs through close contact with infected birds without protective equipment. It can also occur if a person touches contaminated surfaces and puts their hands in their eyes or mouth, or inhales droplets from the air, the CDC added.
The experts pointed out that unclear how dairy cow infected Texas person. The only other person who contracted the H5N1 virus in the United States was directly involved in the slaughter of birds suspected of being infected with the H5N1 virus, Babcock said.
Sporadic cases of H5N1 in humans have been reported around the world, often in rural areas where people live closely with poultry or other birds. According to the WHO, since 2003, 889 cases and 463 deaths from H5N1 have been recorded in 23 countries.
Once bird flu enters a human, “it almost never spreads to anyone else,” Schaffner said. However, “there are ultra-rare cases of transmission from a very sick person with bird flu to a family member or caregiver.”
The contemporary H5N1 viruses currently spreading in birds have not caused any human transmission, according to the CDC.
When this occurs, it does not lead to continued spread between people “because the virus does not have the (genetic) ability to spread easily from person to person,” Schaffner added.
“This strain of bird flu has been around for about a decade and has not yet acquired this ability to spread easily from person to person, fortunately. This should reassure us, but also keep us on alert in the field of public health,” Schaffner said.
Is there a risk of contracting bird flu from eating eggs?
There is no evidence that people can get bird flu from food that has been properly prepared and cooked, and it is safe to eat eggs, chicken and beef, and drink pasteurized milkthe experts added.
“We have not seen cases that have been due to ingesting animal products or animals that may have been infected,” Babcock mentioned.
Herds of infected dairy cows that have been detected are quarantined and their milk is being discarded, Schaffner said.
The commercial milk supply in the country remains safe, the USDA mentioned in a statement. The US Food and Drug Administration (FDA) said it currently has no concerns about the safety of pasteurized dairy products, including pasteurized cheese.
“The pasteurization process in the United States maintains the safety of the milk supply,” Babcock said. Pasteurization heats milk to a temperature high enough to kill bacteria and viruses, including the flu.
Drinking unpasteurized or “raw” milk, increasingly fashionable, is associated with various dangers of infectious diseases, Schaffner said. “I discourage people from drinking raw milk,” he insisted.
According to the FDA, the risk of a human being infected by eating eggs from poultry infected with the H5N1 virus is low, and safeguards are in place to identify infected birds and remove their eggs from the market.
Products from infected animals may end up in the food supply, Babcock said, but the risk to humans remains very low. Properly storing and cooking food reduces that risk even further.
Although cattle are not implicated in this outbreak, Schaffner recommended cooking meat to a safe internal temperature. The FDA suggested cooking eggs until the white and yolk are firm.
“There are other reasons why you should not eat raw eggs (or meat), because they can carry many different pathogens,” Babcock insisted.
What happens if a human being contracts bird flu?
Experts noted that the severity of bird flu infections in humans can vary. According to the CDC, some people have no symptoms or only mild symptoms, while others develop severe illness. “It can be a serious infection with a high mortality rate,” Schaffner said.
The Texas patient had a mild infection, with red eyes as the only symptom, the CDC explained. “It wasn't even a respiratory infection. It was conjunctivitis,” Schaffner said.
The patient was treated with flu antivirals and is recovering. “We have antiviral drugs, the same ones we use to treat the common flu, that work against this strain of bird flu,” Schaffner added.
The other human case of H5N1 in the country, during 2022, was also a mild infection, Babcock said.
Symptoms of bird flu in humans
According to the CDC and experts, recorded signs and symptoms of bird flu in humans include:
- Fever
- Cough
- runny nose
- Muscle or body pain
- Headache
- Fatigue
- Difficulty breathing
- Redness or inflammation of the eyes (conjunctivitis)
- Diarrhea
- Nausea
Bird flu in humans may look like a normal flu or upper respiratory infection, Babcock said, or a person may have no obvious symptoms. It can also cause pneumonia, respiratory failure, and other complications. “There is everything,” he said.
There is no way to diagnose a bird flu infection from symptoms alone, so laboratory testing is necessary, the CDC said.
Do patients infected with bird flu recover?
Yes, it is possible to recover from bird flu. The recently infected human in Texas was treated with flu antivirals and is doing so. The Colorado patient infected in 2022 did as well.
Around the world, bird flu symptoms have ranged from mild to severe, resulting in death in some cases, according to the CDC.
How to protect yourself from bird flu?
Although the risk of contracting bird flu is low, the CDC recommended the following protective measures:
- Avoid visiting poultry farms if possible.
- If you visit, wear a mask and avoid touching the birds.
- Avoid sick or dead birds.
- Maintain good hand hygiene.
- Do not eat raw or undercooked poultry.
- Visit a doctor if you become ill after coming into contact with birds.
