What is avian influenza (bird flu)?

AI virus

Avian influenza virus

If you keep chickens, or another type of poultry, you should know about avian influenza, commonly called bird flu. Avian is another term for bird, and influenza is another term for the flu. Just as you can get the flu, birds can also get the flu. But it is not the same type of flu. Typically humans get human flu and birds get bird flu. It is rare for people to get bird flu, although it has happened in China and neighboring countries.

There are many kinds of flu viruses, and they change all the time. That’s why you need to get a flu shot every year. The type of flu you get vaccinated for one year may not keep you from getting the flu being passed around the next year. The same is the case with birds. There are many different types of bird flu. But there’s no vaccine for them! How do you tell one flu type from another? Flu is caused by a virus. The virus has projections from the surface called hemagglutinin and neuraminidase. Big words! We just refer to them as H and N. There are sixteen types of H and nine of N. That is a lot of possible combinations!

To complicate things, even with the same combinations of H and N, the viruses can be classified as high path or low path. In the case of a high path virus, a lot of birds die in an infected flock. With a low path virus, the number of birds that die can be very low. The problem with low path viruses is that they can mutate (change characteristics) and become high path very easily. That’s why, in both cases, all the birds in the flock have to be killed and disposed of to prevent spreading of the virus. The worst types of virus are the H5 and H7 because the low path types of these viruses mutate very easily to the high path type.

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Dr. Jacquie Jacob
University of Kentucky