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Cold, Flu, & Cough Health Center

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Avian Influenza (Bird Flu) - Topic Overview

What is bird flu?

Bird flu is an infection caused by a certain kind of avian influenza virus. Although there are many kinds of bird flu, the most common kinds that concern health workers are H5N1 and H7N9 bird flu viruses. These viruses are found in wild birds. Most of the time, wild birds don't get sick from the virus. But wild birds can easily pass the virus to birds that are being raised for food, such as chickens, ducks, and turkeys. The virus can cause them to get very sick.

Usually bird flu virus is not passed from birds to people. But since 1997, some people have become sick with this serious, deadly kind of bird flu. Most of these infections have been in Asian countries among people who have had close contact with birds raised on farms.

What causes bird flu?

Bird flu is caused by a virus. After a wild bird infects a farm-raised bird, the virus can easily and quickly spread among hundreds or thousands of birds. Sick birds must then be killed to stop the virus from spreading.

People who come into contact with sick chickens, ducks, or turkeys are more likely to get the virus. Bird flu virus can be passed through bird droppings and saliva on surfaces such as cages, tractors, and other farm equipment.

Most people don't need to worry about getting sick with bird flu virus. You cannot get bird flu from eating fully cooked chicken, turkey, or duck, because heat kills the virus.

Why are people so worried about bird flu?

In a few cases, bird flu was passed from one person to another person, not from a bird to a person. But this was very rare. The bird flu virus can make people sicker than other kinds of flu viruses. Even though only a few hundred people are known to have been sick with bird flu, more than half of them have died.

Experts also worry because the bird flu virus is so different from other flu viruses that our bodies do not have immunity against it. Not having immunity means that our bodies have a hard time fighting the virus. It also means that anyone, including those who are otherwise very healthy, can get seriously ill if he or she gets bird flu.

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