Tuesday, October 18, 2005
Bird flu is the popular name for the illness caused by the H5N1 virus, one of hundreds of types of avian influenza viruses. Many wild birds carry flu viruses that cause them no illness. These viruses sometimes mix and exchange genes, creating new strains. One group rapidly kills domestic chickens and some species of wild birds. The H5N1 virus is in this group.
Q: What is bird flu?
A: Avian influenza, or bird flu, is a virus that is highly contagious among wild birds and often fatal to domesticated birds and poultry. The H5N1 strain was first detected in humans in 1997 and has killed 60 people in Southeast Asia since 2003.
Q: Where did H5N1 start?
A: It emerged in southern China in 1996 and caused a large outbreak in Hong Kong in 1997 that killed six people. Scientists believe genetic mutations of H5N1 have allowed easier infection of mammals.
HUMAN INFECTIONS: So far, nearly all human victims of H5N1 had direct contact with birds, and no H5N1 strain has passed easily from person to person.
FELINE INFECTIONS: Domestic cats in Germany and Austria have contracted H5N1 bird flu, probably by eating wild birds.
Q: What are the symptoms of bird flu in humans?
A: Human symptoms can include typical flu-like symptoms, like fever, cough, sore throat and muscle aches, as well as eye infections, pneumonia and severe respiratory illness.
Q: How do humans get bird flu?
A: The virus is spread through contact with infected birds or contaminated surfaces. However, risk of infection in humans is low and person-to-person transmission is rare.
Q: How do all flu viruses work?
A: Each flu virus has two proteins studding its surface. They help the virus penetrate cells, initiating infection.
Known collectively as "antigens," the proteins are also what the immune system recognizes when it mounts a defense. Variations in the shape of the proteins, determined by the virus' genes, give each flu strain its particular identity.
Q: What is the pandemic threat?
A: Scientists worry the H5N1 virus will mutate and become more easily spread from person to person, spurring a pandemic.
Q: How can doctors detect bird flu?
A: With a blood test.
Q: Is there a vaccine for bird flu?
A: There is no commercial vaccine currently available, but clinical trials for a vaccine against the H5N1 virus are underway.
Q: How is bird flu treated?
A: Research suggests that human flu drugs can be effective in treating H5N1 if administered quickly. But the virus can be resistant to such drugs.
Source: Centers for Disease Control and Prevention, National Institutes of Health, Food and Agriculture Organization of the United Nations, World Health Organization, World Organization for Animal Health, International Society for Infectious Diseases