Influenza A: H5N1

A “bird flu”, H5N1 can also cause illness in mammals, including humans

Influenza A: H5N1 Virus

Learn about H5N1, how it can spread to people, and prevention strategies

H5N1 is an influenza (flu) virus that can cause severe illness and death in wild birds, commercial poultry, and backyard flocks. Though it is a type of avian influenza, or “bird flu”, H5N1 can also cause illness in mammals, including humans. In 2024, the U.S. is experiencing a multi-state outbreak of H5N1 affecting birds, cows, and some humans working with infected animals. So far, there are not any known cases of H5N1 passing from person to person and risk of infection to the general public is low.

How H5N1 Spreads to People

Close or prolonged unprotected contact with infected live or dead birds and mammals, or their feces/mucous/saliva/raw body products
Exposure to H5N1-contaminated environments. H5N1 flu virus can get into a person’s eyes, nose or mouth when virus is in the air (such as in air particles or dust), is inhaled from contaminated air, or when a person touches something contaminated by virus and then touches their mouth, eyes, or nose.

Symptoms & Prevention

Symptoms

Illness in people infected with H5N1 have ranged from mild upper respiratory symptoms to severe (such as pneumonia and organ failure) and could result in death. Symptoms might include:

Conjunctivitis
Fever
Feeling feverish/chills
Cough
Sore throat
Headaches
Runny or stuffy nose
Muscle or body aches
Diarrhea
Difficulty breathing/shortness of breath

Prevention of H5N1 in Humans

Avoid direct unprotected contact with wild birds, backyard flocks, and other animals that may be sick, have died, or are suspected or known to have H5N1 virus infection
Do not touch surfaces that may be contaminated by wild or domestic birds or other animals with confirmed or suspected H5N1 virus infection
People should not prepare or eat uncooked or undercooked food or related uncooked food products, such as unpasteurized (raw) milk, or raw cheeses, from animals with suspected or confirmed H5N1 flu virus
People exposed to H5N1 flu virus-infected birds or other animals (including people wearing recommended personal protective equipment) should monitor themselves for new respiratory illness symptoms, including conjunctivitis (eye redness), beginning after their first exposure and for 10 days after their last exposure. If a symptom develops, get medical testing and evaluation; treatment may be available for H5N1 flu infection.

Precautions for Persons at Higher Risk of H5N1 Flu Virus Exposure

Poultry farmers and poultry workers, backyard bird flock owners, livestock farmers and workers, veterinarians and veterinary staff, and emergency responders should avoid unprotected direct physical contact or close exposure with animals and materials potentially infected or confirmed to be infected with H5N1 flu virus, including: sick birds, livestock, or other animals; carcasses of birds, livestock, or other animals; feces or litter; raw milk; surfaces and water (e.g., ponds, waterers, buckets, pans, troughs) that might be contaminated with animal excretions.
Farmers, workers, and emergency responders should wear appropriate PPE when in direct or close physical contact with sick birds, livestock, or other animals, carcasses, feces, litter, raw milk, or surfaces and water that might be contaminated with animal excretions from potentially or confirmed infected birds, livestock, or other animals, and when entering not yet disinfected buildings where these animals or materials are or were.