Avian flu, or bird flu, refers to a group of diseases that result from infections with specific influenza viruses. These viruses infect birds but rarely spread to humans.
Animal influenza viruses are different from seasonal human influenza viruses. These types of zoonotic viruses do not easily transmit between humans. However, occasionally zoonotic influenza viruses may infect humans and can cause disease that can range from mild illness to death.
Birds are the natural hosts for avian influenza viruses. One virus that causes bird flu is called H5N1. The H5N1 virus can cause severe flu with a high mortality rate. However, according to the Centers for Disease Control and Prevention (CDC), transmission among humans is rare.
It is not easy for the H5N1 virus to transmit from animals to humans. It is even harder for the virus to pass from person to person.
However, if a person with seasonal flu then develops this bird flu, the H5N1 virus may be able to exchange genetic information with the seasonal flu virus. Additionally, other viral genetic mutations can occur in nature and impact the transmissibility of the virus. If this happens, the H5N1 virus could gain further ability to spread among people.
A strain of avian flu virus that develops greater ability to spread among humans could have serious consequences. Controlling outbreaks of bird flu in animals and humans can help keep the virus from developing this capacity and prevent further spread that could lead to a pandemic.
The Food and Agriculture Organization of the United Nations state that the H5N1 virus is rapidly spreading between birds, causing more than 30 million bird deaths in the U.S. this year.
However, at present, the
In early 2025, the Louisiana Department of Health reported that one person in the U.S. died of H5N1 bird flu. However, they add that the individual had underlying medical conditions and had exposure to wild birds. They also note there is no evidence of person-to-person transmission, and there are no additional human cases of H5N1 in Louisiana.
Type A strains of the influenza virus, including H5N1, cause avian flu, or bird flu. The H5N1 virus can infect several types of birds. Authorities have mostly reported the disease in farmed poultry, such as chickens, geese, turkeys, and ducks.
So far, the virus has shown no signs of changing genetically to spread more efficiently among humans. However, due to the severity of the illness that the virus can cause, authorities continue to monitor for these genetic changes. H5N1 bird flu is fatal in 54% of cases.
The virus spreads easily among birds through their saliva, nasal secretions, feces, and feed. They can
The first outbreak of H5N1 avian flu in humans occurred in 1997 in Hong Kong. Until now, very few cases of human-to-human transmission have occurred. From 2003 to 2024, there were less than 1,000 global cases of human infection with the H5N1 virus. The
The “incubation period” of a virus is the amount of time between the infection and the host developing symptoms. The virus may be contagious during this time.
A
H5N1 bird flu can cause severe
- a fever of above 100.4ºF (38ºC)
- a cough
- muscle aches
The following
Some people with H5N1 bird flu develop severe respiratory problems, including pneumonia and breathlessness.
The condition of a person with H5N1 avian flu can deteriorate rapidly. They may experience respiratory failure and multiple organ failure, leading to death.
Humans can acquire the infection and develop the illness after coming into unprotected contact with birds who are carrying the virus. Human-to-human transmission is rare.
The following activities may lead to the illness in humans:
- touching infected birds
- touching or breathing in feces or other secretions of infected birds
- preparing infected poultry for cooking
- slaughtering or butchering infected poultry
- handling birds for sale
- attending markets that sell live birds
The infection can
Eating cooked poultry or eggs does not cause infection. However, it is important to cook poultry until its internal temperature is at least 165º F (74º C) and eggs until both the whites and yolks are firm.
Bird droppings may contain the virus and can contaminate feed, equipment, vehicles, shoes, clothing, soil, dust, and water. The bodies, and particularly the feet, of animals can also carry the H5N1 virus.
Receiving a diagnosis of H5N1 avian flu early can lead to a better outlook.
Before arriving at a diagnosis, the doctor will:
- consider the person’s symptoms
- look for signs of bird flu
- ask about recent travel
- ask about any contact with birds
- collect a respiratory specimen and send it to a lab for analysis
In 2009, the FDA approved the
The test can identify a specific protein, called NS1, which indicates the presence of the virus.
Because H5N1 avian flu is rare, a physician would not expect to make this diagnosis, unless the person has been in contact with birds or recently stayed in a place where H5N1 infection is likely.
According to the World Health Organization (WHO), antiviral medications can
The
People for whom H5N1 bird flu causes gastrointestinal problems may not be able to absorb the drug as effectively as people who do not experience abdominal pain, diarrhea, or vomiting.
Anyone who has diagnosed or suspected avian flu should remain isolated, at home or in a hospital.
Apart from taking Tamiflu, healthcare professionals advise people to:
- rest
- drink plenty of fluids
- eat a balanced and healthful diet
- take other medications to help manage the pain and fever
Complications, such as bacterial pneumonia, are common in people with H5N1 avian flu. Anyone with bacterial pneumonia will need to take antibiotics, and some people may need supplemental oxygen.
It is not possible to prevent bird flu from spreading. However, authorities can help communities prepare for possible infections by monitoring bird migration patterns.
Routine vaccination is available for seasonal flu, but not bird flu.
In the U.S., the FDA have given approval for
Individuals can minimize the spread of bird flu by taking precautions. These include:
- Hand hygiene: Wash the hands regularly with warm water and soap before and after using the bathroom, handling food, or coughing.
- Coughing: It is best to cough into an elbow or tissue and carefully dispose of used tissues — also, touching a surface after coughing into the hands can leave the virus on the surface, allowing it to spread.
- Isolation: Those who have symptoms should stay away from public places and avoid contact with people, whenever possible.
The
Precautions around birds
When preparing meals, do not use the same utensils for cooked and raw meats. Before and after handling raw poultry, it is essential to wash the hands with soap and water.
Avoid dead or sick birds. To remove dead birds, call the relevant local authority. People who work with domestic birds should follow local and national guidelines.
Anyone traveling to an area in which avian flu may be active should avoid:
- bird feces
- live animal markets
- poultry farms
Being aware of the risks of infections — and taking all necessary precautions — is an effective way to avoid these illnesses.
People in areas with confirmed outbreaks of H5N1 avian flu should take every precaution and seek urgent medical advice if they start to notice symptoms, especially if they handle poultry or birds on a regular basis.
H5N1 bird flu can cause severe symptoms, and it has a high death rate. However, the virus does not transmit easily among humans, and the risk of a pandemic is low.
There is no routine vaccine available, but maintaining hand hygiene, isolating, and coughing only into an elbow or tissue can reduce the chances of acquiring or transmitting the virus.