H5N1 bird flu, or avian influenza, in Florida: What to know

Avian influenza, also known as bird flu, is a disease that primarily affects birds. It is caused by a virus related to those that cause seasonal flu. A subtype of the bird flu virus known as H5N1 can infect mammals, including humans. Certain strains of H5N1 can be highly lethal. About half of people diagnosed with H5N1 since 2003 have died from the virus.

The strains of H5N1 circulating currently in the U.S. do not easily transmit from person to person and does not cause severe illness in otherwise healthy people. This is why H5N1 is considered to pose a low public health risk. If H5N1 mutates to gain these features, however, it could trigger a pandemic. This is why scientists are monitoring H5N1 closely.

Bird flu basics

Highly pathogenic avian influenza virus, or H5N1, was first identified in 1996 and quickly spread globally. H5N1 is capable of infecting many species of mammals, including people. Most bird flu cases in humans in the U.S. have occurred in farm workers. In most cases, symptoms were mild and commonly included conjunctivitis, fever and/or respiratory problems. The current strains of H5N1 circulating in U.S. dairy cows have not been as lethal to people as some other H5N1 strains, but they could mutate to become more severe and/or contagious.

H5N1 is a subtype of bird flu that may also be referred to as avian influenza H5N1, A(H5N1), H5 bird flu and highly pathogenic avian influenza (HPAI or HPAI H5N1). It belongs to a group of pathogens known as influenza A viruses, which also include those that can cause the common flu.

H5N1 is regarded as highly pathogenic due to its ability to infect and kill poultry quickly. The virus can decimate flocks within 48 hours. Nearly 200 million chickens in the U.S. have been infected with H5N1 since 2022. A virus that is highly pathogenic in poultry is not necessarily highly pathogenic in humans.

While H5N1 primarily infects wild birds and poultry, it can also infect other animals. These outbreaks have been sporadic. H5N1 has been detected in dozens of mammal species, including bears, foxes, sea lions, cats, dogs, cows, pigs and dolphins.

Influenza A viruses mutate frequently, which means that H5N1 could develop the ability to cause more serious illness in people and/or transmit from person to person easily. The more the virus spreads and the more kinds of animals it infects, the greater its chances of acquiring these characteristics. Scientists are monitoring the virus closely for these kinds of mutations.

Bird flu in Florida

Although H5N1 has not been identified in Florida dairy cattle, it has been found previously in other animals in the state, including wild birds in 35 counties and backyard chickens. Wild birds presumed or confirmed to be infected include waterfowl, waterbirds and raptors, among others. No human cases of H5N1 have occurred in Florida.

Bird flu transmission

At least 70 people in the U.S. have tested positive for bird flu since monitoring began in 2022. Most of these cases occurred in people working with poultry or dairy cows. Three people, however, had no immediately known exposure to animals. One infected person in Louisiana died.

There has been no known person-to-person transmission of bird flu in the U.S.

Symptoms of bird flu

Symptoms of bird flu vary, and most U.S. cases have been mild. Some people who tested positive for H5N1 showed no sign of being sick. Eye redness and/or irritation is the most common symptom, occurring in more than 90% of cases. For a third of these people, this was the only sign of bird flu. Others experienced typical flu-like symptoms, such as fever or respiratory problems.

Complications from severe infections, however, can include pneumonia, respiratory failure, organ failure, sepsis and brain inflammation.

Symptoms in people:

• conjunctivitis, or eye infection
• fever
• cough
• sore throat
• nasal congestion
• aches
• fatigue
• intestinal problems, such as diarrhea, nausea or vomiting
• respiratory problems
• altered consciousness
• seizures

People most vulnerable to H5N1 infections

People who work closely with dairy cows and poultry are the most vulnerable to infection. Most U.S. cases have occurred in agricultural workers.

Symptoms generally appear two to seven days after infection and usually last less than two weeks. People are most contagious in the first few days of infection; however, in cases of severe illness, they may be contagious for several weeks.

Bird flu diagnosis

Influenza A testing can detect H5N1 in people. Healthcare providers should test patients with symptoms of respiratory illness for bird flu.

Bird flu treatment

Bird flu can be treated with oseltamivir, also known as Tamiflu, a common antiviral treatment for flu.

Three vaccines for bird flu have been licensed in the U.S. for individuals at high risk, but they are not widely available. They were also developed before the recent outbreak and may offer limited protection against the current strains of H5N1.

Clinical trials for new vaccines are underway.

Bird flu prevention

Close contact with infected animals and their environment is the primary route of transmission of H5N1 in the U.S. People can get infected by touching infected animals and then touching their eyes, nose or mouth, or by inhaling the virus.

A seasonal flu vaccination does not protect against H5N1. However, getting a seasonal flu vaccination can reduce the chance of being infected with H5N1 and seasonal flu at the same time. Because flu viruses can swap genetic material, a simultaneous seasonal flu and H5N1 infection could result in the H5N1 virus acquiring the ability to transmit more easily between people.

You can reduce your risk of infection by avoiding raw, unpasteurized milk, or boiling it before consumption, and cooking eggs, poultry and beef thoroughly. Do not touch

sick or dead animals. If you must handle sick or dead animals, use personal protective equipment. Minimize contact with wild birds. Report bird deaths to the Florida Fish and Wildlife Conservation Commission.

Protecting pets and livestock

H5N1 is particularly deadly to cats. You can reduce your cat’s potential exposure to H5N1 by keeping it away from birds, especially waterfowl and poultry, cows and other animals. Some cats have become sick after eating raw food or drinking raw milk contaminated with the H5N1 virus.

If your cat is sick, immediately seek veterinary care. Symptoms of bird flu in cats include fever, lethargy, loss of appetite, red or inflamed eyes, discharge from the nose or eyes, trouble breathing and neurological problems, including tremors and blindness.

Dogs can also contract the virus but appear to be less prone to severe illness.

Symptoms of bird flu in cows include decreased milk production, loss of appetite, breathing problems, lethargy and sudden death. Symptoms of bird flu in poultry include respiratory and digestive problems, discoloration in the head and legs, swelling around the head, neck and eyes and sudden death. Seek immediate veterinary care for sick animals.

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