Bird flu, or avian flu, is a type of infection that occurs mainly in birds. Most bird flu viruses don’t infect humans, but some strains — particularly H5N1 and H7N9 — can, in rare cases, spread to humans and cause serious illnesses, according to the Centers for Disease Control and Prevention (CDC). (1)
Bird flu is transmitted to humans when these viruses, which are part of a group called avian influenza A viruses, travel from the saliva, mucus, or droppings of an infected bird into a person’s eyes, nose, or mouth. Humans can become infected by breathing in the virus, which can survive in air droplets or dust, or touching a surface that’s harboring the virus and transferring it to eyes, nose, or mouth.
Rarely, the virus also can spread from person to person, notes the National Library of Medicine. (2)
Signs and Symptoms of Bird Flu
The symptoms of bird flu typically begin within two to five days after catching the virus, according to the World Health Organization (WHO). (3) They’re often similar to those of the seasonal flu, and can range from mild to severe. They typically include:
- Fever greater than 100.4 degrees F (38 degrees C)
- Sore throat
- Difficulty breathing
- Nausea and vomiting
- Muscle aches
- Abdominal pain
- Bleeding from the nose or gums
Gastrointestinal symptoms such as nausea, vomiting, and diarrhea are more commonly seen in people who have the H5N1 infection; conjunctivitis is more commonly seen in people who are affected by H7 forms of the virus. (3)
Causes and Risk Factors of Bird Flu
Bird flu is spread through contact with both wild birds and domestic poultry, such as chickens, turkey, and ducks, per the Mayo Clinic. (4)
While bird flu infections are rare, most of them occur in people who’ve had unprotected contact with an infected bird or a contaminated surface. There have, however, been some instances in which a person has become infected without making direct contact with a bird.
More rarely, the virus has spread from person-to-person, but this type of transmission has been limited, and does not seem to happen easily, notes the CDC. (5)
Open-air markets can also be a source of bird flu, since eggs and birds can be sold in unsanitary conditions.
There have been a few cases of H5N1 in humans who’ve eaten food made with raw, contaminated poultry blood, but there’s no evidence that people have been infected with bird flu from eating properly cooked poultry. (3) Eating undercooked poultry has also been associated with infections other than influenza, including salmonella (1).
Some people are more at risk than others for being very sickened with bird flu, including pregnant women, adults over the age of 65, and people with weakened immune systems. (2)
How Is Bird Flu Diagnosed?
Bird flu can’t be diagnosed based on symptoms alone. To diagnose bird flu, a healthcare professional will take a swab from a person’s nose or throat and send the sample to a lab, which can use a molecular test to detect the virus.
The test is most accurate when the sample is taken within the first few days of a person’s illness; it can be hard to detect the virus in someone who is no longer very ill or has fully recovered. It may be possible, however, to find antibodies that a person has produced to fight off the virus. (1)
Prognosis of Bird Flu
While symptoms may be mild, more severe cases of bird flu can be deadly. For those patients hospitalized with avian influenza, mortality is more than 50 percent for all of the strains combined. The mortality rate for H5N1 has been estimated to be 60 percent, according to Stat Pearls. (6) The mortality rate for H7N9 is around 40 percent, according to research published in August 2020 in Emerging Infectious Diseases. (7)
Duration of Bird Flu
The average incubation period of bird flu H5N1 is two to five days, though it can last up to 17 days. (3) For H7N9, the average incubation period is five days, and can last up to 10 days. (3) Both viruses have a longer incubation time than that of seasonal influenza.
The World Health Organization says that people with bird flu should be treated with antiviral medications for at least five days, but can continue taking them until their symptoms improve. (3)
Treatment and Medication Options for Bird Flu
Bird flu in humans can be treated with antiviral drugs, which can hamper the viruses’ ability to replicate and help people recover from the illness.
Antiviral medications can work best when they’re prescribed as soon as possible, ideally within 48 hours after the symptoms appear. The medications used to treat bird flu include:
- Tamiflu (oseltamivir)
- Relenza (zanamivir)
- Rapivab (peramivir)
But the H7N9 and H5N1 viruses have become resistant to the antiviral drugs Gocovri (amantadine) and Flumadine (rimantadine).
Prevention of Bird Flu
There is no widely available vaccine to prevent bird flu in the United States. The best way to prevent bird flu is to avoid the sources of the exposure.
People who work with poultry should follow infection control practices, such as wearing personal protective equipment and following proper hand hygiene protocols.
Wild birds can also be a source of the infection, so it’s best to let local or state agencies dispose of a dead bird. If a large number of birds are dying in the same area, a wildlife organization will likely investigate the cause. People shouldn’t get too close to birds, and should avoid touching surfaces that are contaminated with bird droppings.
The CDC tells people who are traveling to countries with avian flu to avoid visiting areas where birds are raised or sold, including poultry farms and open-air market, and to avoid visiting places where eggs and birds are sold in unsanitary conditions. (1) They also advise making sure that any poultry or eggs you eat are fully cooked and to avoid dishes that contain blood from animals. (1)
People who’ve been in contact with an infected bird may be given antivirals preventatively, as these medications can also help prevent infection.
The U.S. Food and Drug Administration has approved two vaccines to prevent the H5N1 bird flu virus, but they are both being held in reserve by the U.S. government in case an outbreak occurs. (8)
The seasonal flu vaccine doesn’t protect against avian flu.
Research and Statistics: How Many People Have Bird Flu
Bird flu virus H5N1 was first reported to infect humans in 1997 during an outbreak among poultry in Hong Kong, and became widespread in 2003.
In total, says the CDC, this strain of bird flu has been detected in poultry and wild birds in more than 50 countries in Africa, Asia, Europe, and the Middle East. (9)
In January 2014, Canada reported the first human infection of H5N1 in the Americas, which occurred in a person who recently returned from China. (9)
Bird flu virus H7N9 was first reported to infect humans in China in March 2013.
Since 2013, according to the WHO, more than 1,500 people have been infected with H7N9. (10) Most of these cases occurred in China, but some infections been reported in other countries among travelers who had just returned from China, notes the CDC. (11)
In 2015, a husband and wife in the United States became ill with H7N9 after a trip to China; the United States has not had any cases of H5N1, per the CDC. (12) However, it has had a few other types of bird flu infections in humans. For instance, in 2002, a person in Virginia working to dispose of poultry infected with H7N2 there developed an infection, according to research published in July 2018 Influenza and Other Respiratory Viruses. (13) In 2016, there was an outbreak of H7N2 in New York City among cats in an animal shelter, and one person who was exposed to the sick cats became infected, notes the CDC. (14)
Related Conditions and Causes of Bird Flu
As mentioned above, bird flu can lead to pneumonia. It may also lead to encephalitis (inflammation of the brain).
Resources We Love
Favorite Organizations for Essential Information
Centers for Disease Control and Prevention (CDC)
The CDC’s website provides updates on bird flu activity worldwide. The site details who may be most likely to contract the virus and what precautions at-risk people can take to avoid becoming sick.
World Health Organization (WHO)
The WHO works with countries around the world to combat diseases such as influenza. Their website provides information about bird flu and other zoonotic infections.
Editorial Sources and Fact-Checking
- Influenza: Bird Flu in People. Centers for Disease Control and Prevention. April 17, 2017.
- Bird Flu. U.S. National Library of Medicine. February 15, 2017.
- Influenza (Avian and Other Zoonotic). World Health Organization. November 13, 2018.
- Bird Flu (Avian Influenza). Mayo Clinic. November 1 2017.
- Examples of Human Infections With Avian Influenza A Viruses With Possible Limited, Non-Sustained Human-to-Human Transmission. Centers for Disease Control and Prevention. April 10, 2017.
- Sendor A, Weerasuriya D, Sapra A. StatPearls. June 3, 2020.
- Zhang J, Ye H, Li H, et al. Evolution and Antigenic Drift of Influenza A (H7N9) Viruses, China, 2017–2019. Emerging Infectious Diseases. August 2020.
- Vaccines Licensed for Use in the United States. U.S. Food and Drug Administration. April 24, 2020.
- Asian Avian Influenza A (H5N1). Centers for Disease Control and Prevention. December 12, 2018.
- Human Infection With Avian Influenza A(H7N9) Virus – China: Update. World Health Organization. September 5, 2018.
- Asian Lineage Avian Influenza A (H7N9) Virus. Centers for Disease Control and Prevention. December 7, 2018.
- Influenza: Current Situation. Centers for Disease Control and Prevention. March 17, 2015.
- Terebuh P, Adija A, Edwards L, et al. Human Infection With Avian Influenza A (H7N2) Virus-Virginia, 2002. Influenza and Other Respiratory Viruses. July 2018.
- Avian Influenza A (H7N2) in Cats in Animal Shelters in NY; One Human Infection. Centers for Disease Control and Prevention. December 22, 2016.