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Bird Flu

(Avian Flu; Avian Influenza)


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Mar 2021| Content last modified Mar 2021

Bird flu is a viral infection with strains of influenza virus that normally occur in wild birds and domestic poultry.

  • The bird flu virus, which rarely spreads from animals to people, spreads to people mainly when the genetic material of the virus mutates.
  • Nearly all people who have been infected with bird flu have had close contact with an infected bird (it almost never spreads from one person to another).
  • People may have extreme difficulty breathing and flu-like symptoms.
  • To diagnose bird flu, doctors test a sample of secretions from the nose or throat.
  • Bird flu is treated with antiviral drugs.

(See also Influenza.)

Bird flu is caused by several strains of influenza A virus that normally infect wild birds. The infection can be easily spread to domestic birds. However, it rarely spreads from animals to people. It spreads to people mainly when the genetic material of the virus changes (mutates), enabling the virus to attach to cells in the human respiratory tract. Nearly all people who have been infected with bird flu have had close contact with an infected bird. Bird flu almost never spreads from person to person. However, experts are concerned that additional mutations could enable the virus to spread more easily from person to person. Then, bird flu could spread rapidly and widely, causing a major worldwide epidemic (a pandemic).

Human infection with the avian influenza H5N1 (see influenza types and strains) first occurred in Hong Kong in 1997 and then spread to Vietnam, then to Indonesia, Cambodia, China, Thailand, Turkey, Azerbaijan, Djibouti, Egypt, and Iraq. Since 2003, more than 860 cases of human H5N1 infection with 454 deaths have been reported in 16 countries in Asia, Africa, the Pacific, Europe, and the Near East. One human infection was confirmed in 2019, and it was in Nepal.

In 2013, an outbreak began in southeastern China. It involved the avian flu strain H7N9. Worldwide, over 1500 human cases and at least 615 deaths have been reported to the World Health Organization since 2013. The infection has occurred mainly in communities that consume poultry from live poultry markets. There was 1 case confirmed in mainland China in 2019.

China is vaccinating poultry with a vaccine to prevent H5 and H7 flu viruses. This vaccination program can help prevent the bird flu virus from spreading from wild birds to domestic birds. Domestic birds are more likely to come in contact with people and spread the virus to them.

Other strains of the avian flu virus have also caused sporadic outbreaks of infection in people. However, in these outbreaks, the virus has not spread from person to person.

Symptoms of Bird Flu

H5N1 and H7N9, which cause most cases of bird flu in people, have similar effects.

People may have extreme difficulty breathing and flu-like symptoms (such as fever, cough, sore throat, and muscle aches). Some people have conjunctivitis or pneumonia.

In people with severe symptoms, the death rate is high.

Diagnosis of Bird Flu

  • Testing of a sample taken the nose or throat

People should contact a doctor if they have flu-like symptoms plus one of the following:

  • They have had contact with birds in an area where birds are known to carry the infection.
  • They have had contact with a person infected with bird flu.

The doctor can send a sample taken by swabbing the nose or throat to be tested.

Prevention of Bird Flu

Spread is contained by identifying and destroying infected flocks of domestic birds.

A vaccine for H5N1 bird flu is being stockpiled by the United States government in case of an epidemic. The standard vaccine for influenza does not prevent bird flu.

Treatment of Bird Flu

  • Antiviral drugs

Infected people are given oseltamivir or zanamivir (antiviral drugs that are used to treat influenza). These drugs usually improve survival.

Drugs Mentioned In This Article

Generic Name Select Brand Names
oseltamivir TAMIFLU
zanamivir RELENZA

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