Avian influenza A(H5N1): Symptoms and treatment

Avian influenza is a contagious viral infection that mainly affects birds but can sometimes infect humans and other mammals. There are many types of avian influenza, which are all caused by various strains of type A influenza virus (e.g., H5N1, H7N3, H9N2). Avian influenza A(H5N1) illness is caused by the avian influenza A(H5N1) virus.

On this page

• Symptoms of avian influenza A(H5N1)
• If you become ill
• Diagnosing avian influenza A(H5N1)
• Treating avian influenza A(H5N1)

Symptoms of avian influenza A(H5N1)

Human infections with avian influenza A(H5N1) are rare and usually occur after close contact with infected birds or highly contaminated environments such as poultry farms or live animal markets. Infection may also occur after exposure to other infected animals, including wildlife and livestock, such as cattle. Learn more about who is most at risk of exposure and infection.

Some infected people may not develop any symptoms at all. However, if symptoms do develop, illness can range from mild to very severe, including death. It usually takes from 1 to 5 days, and occasionally longer, for symptoms to appear after exposure.

Symptoms often start with:

• cough
• shortness of breath
• fever
• aching muscles
• headache

Other early symptoms may include:

• diarrhea
• runny nose
• sore throat
• fatigue
• conjunctivitis (red eyes)
• bleeding gums

In rare cases, the infection may progress quickly to:

• severe respiratory illness, which can include:
• difficulty breathing
• pneumonia
• acute respiratory distress syndrome
• neurological changes (changed mental state or seizures)

In severe cases, the infection may also lead to multi-organ failure, which can include kidney and liver dysfunction and cardiac impairment, and lead to death.

Approximately half of the over 900 human cases reported around the world since 1997 (mostly in Africa and Asia), have been fatal. However, this may be an overestimate given that mild infections can go undetected and under-reported.

If you become ill

Contact a health care provider or your local public health authority immediately if you:

• are showing any of the above symptoms and
• have been exposed to birds, other animals, or contaminated environments such as animal farms or live animal markets, that are suspected to have avian influenza A(H5N1) virus in the 10 days prior to developing symptoms

If you have severe symptoms, call 9-1-1 or your local emergency number immediately.

Tell your health care provider or local public health authority that you may have been exposed to avian influenza.

Isolate away from others and follow measures which help reduce the spread of influenza and other respiratory viruses, including respiratory etiquette (e.g., covering your mouth and nose with a tissue or your elbow when coughing or sneezing), physical distancing, wearing a mask when physical distancing is not possible, regular hand hygiene, improving indoor ventilation (e.g., opening windows), and regularly cleaning and disinfecting of surfaces and objects.

Diagnosing avian influenza A(H5N1)

A laboratory test is required to diagnose avian influenza A(H5N1). It is usually diagnosed by taking a swab from the nose or throat during the first few days of illness. This swab is then sent to a laboratory for testing to identify the type of virus causing the infection.

Treating avian influenza A(H5N1)

Antiviral medications can be used to treat avian influenza A(H5N1). It is important that antiviral medications be taken as early as possible, ideally within 48 hours of getting sick. They can:

• reduce influenza symptoms
• shorten the length of illness
• potentially reduce serious complications

People with severe infection need to be hospitalized.