Sixth Grade
Worksheets
Bird Flu
Bird flu has been around for a long time. So why have scientists and everyday people around the world become so concerned about it recently?
The reason is that bird flu has only affected humans since the 1990s. Before that, bird flu was only known to affect birds.
No one knows when the first birds in the wild became ill from bird flu. The flu first drew attention when it began to affect domestic birds, such as chickens. There were two forms of the virus. One form barely made the chickens sick, and it went unnoticed, too. The other form was much more deadly. The mortality rate of this severe form was almost one hundred percent.
This deadly form of bird flu spread rapidly. It could be carried on farm workers' clothes, and on cages, equipment, and farm vehicles. The only known way to stop an outbreak of this bird flu was to destroy an entire infected flock of chickens.
In the 1990s, bird flu also began to make people sick. People who worked with poultry or who had contact with dead or sick birds seemed to be most at risk. Bird flu made people ill in countries in Europe, Asia, and Africa. China, Egypt, Indonesia, Thailand, and Vietnam were some of the countries where humans were most affected by the flu.
Bird flu is a deadly disease for humans. The disease starts out with symptoms like a fever and a sore throat, but it progresses rapidly to pneumonia. Of the known cases of bird flu in humans, sixty percent of the people infected with the virus have died.
So far, the bird flu virus is not able to pass from person to person. Only a person who had been in contact with infected or dead birds can catch the virus. No one has caught it from other sick people. This is because the bird flu virus was not adapted to humans.
Even though the virus did not make large numbers of people ill, many feared that someday it might. They had a good reason to be afraid, and it had to do with a special property of viruses. Viruses can change, or mutate, very rapidly. There have already been several different strains of bird flu. What if a new strain developed that was adapted to humans? What if it was able to pass directly from human to human?
