Q: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
The 1918, 1957 and and 1968 flu pandemics can be traced back to bird flu mutating with human virus. These pandemics killed scores of people. The panic also stems from the fact that there is no vaccine for H5N1 virus, the bird flu that is currently affecting Asia. Like last year, vaccines for "regular" human flu are in short supply as well.
Under normal circumstances, when the flu hits you're just feverish, achey and fatigued for a few days. When the flu strikes more vulnerable people, like the elderly and very young babies, it can cause respiratory problems and even kill them.
A:
why does the bird flu considered to be such a frightening disease?