Avian Influenza [Bird Flu] Fact Sheet

Wayne County Department of Public Health

Avian Influenza [Bird Flu]
An outbreak of avian influenza, more commonly known as bird flu, is affecting bird populations in countries throughout Asia—Cambodia, China, Hong Kong, Indonesia, Japan, Laos, South Korea, Thailand and Vietnam. The outbreak is caused by H5N1 subtype of influenza A. Type A influenza viruses can infect several animal species, including birds, pigs, horses, seals and whales. However, influenza viruses that infect birds are called “avian influenza viruses.”

Avian influenza usually does not make wild birds sick, but can make domesticated birds very sick and kill them. Avian influenza A viruses do not usually infect humans; however, in 1997 the first instance of direct bird-to-human transmission of H5N1 was documented during an outbreak of avian influenza among poultry in Hong Kong. The virus caused severe respiratory illness in 18 people, including six who died. Since that time there have been other instances of H5N1 infection among humans.

Characteristics of Avian Influenza in Birds
Certain water birds act as hosts of influenza viruses by carrying the virus in their intestines and shedding it. Infected birds shed virus in saliva, other secretions and feces. Avian influenza viruses spread among susceptible birds when they come in contact with contaminated secretions or fecal material from infected birds; however, fecal-to-oral transmission is the most common mode of spread.

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Symptoms of Avian Influenza in Humans
The symptoms of avian influenza in humans have ranged from typical influenza-like symptoms—cough, sore throat, muscle aches, eye infections, pneumonia, acute respiratory distress, viral pneumonia and other severe and life-threatening complications.

Potential for an Influenza Pandemic
All influenza viruses have the potential to change. It is possible that an avian influenza virus could change so that it could infect humans and could spread easily from person-to-person. If an avian virus were able to infect people and gain the ability to spread easily from person-to-person, an “influenza pandemic” could begin. When human infections do occur, public health authorities monitor the situation closely because of concerns about the potential for more widespread infection in the human population.

Avian Influenza Infections in Humans
1997: In Hong Kong, avian influenza A (H5N1) infected both chickens and humans. During this outbreak, 18 people were hospitalized and 6 of them died. To control the outbreak, authorities killed about 1.5 million chickens to remove the source of the virus.

1999: In Hong Kong, cases of avian influenza A [H9N2] were confirmed in 2 children. Both patients recovered, and no additional cases were confirmed. The evidence suggested that poultry was the source of infection and the main mode of transmission was from bird-to-human.

2003: Two cases of avian influenza A [H5N1] infection occurred among members of a Hong Kong family that had traveled to China. One person recovered, the other died.

2003: Avian influenza A [H7N7] infections among poultry workers and their families were confirmed in the Netherlands during an outbreak of avian flu among poultry. More than 80 cases of H7N7 illness were reported, and 1 patient died.

2003: H9N2 infection was confirmed in a child in Hong Kong. The child was hospitalized but recovered.

Source: Centers for Disease Control and Prevention

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