Now scientists are working on vaccines to fight the deadly bird flu H5N1. But these vaccines aren't easy to make. One reason is that the flu virus often mutates. So a vaccine that worked against the flu last year won't protect you very well this year.

Another problem is that it takes years of tests to make sure bird flu vaccines will work on humans without making them sick.

In 2005, a study began testing a possible bird flu vaccine on 450 people. The vaccine uses a type of bird flu that was found in Southeast Asia in 2004. Some of the early results are promising. But as of spring 2007, there is still no vaccine available for H5N1.

—When Birds Get Flu and Cows Go Mad!,
John DiConsiglio

Explain the challenges scientists face with mutating viruses and how they are trying to solve the problem.

The bird flu like other flu is caused by a virus and this virus mutates very fast with time. Mutation is a change in the genetic make up of an organism which in this case, makes them resistant to vaccines that was effective on them not too long ago. Also, available vaccines need to be tried clinically to determine their potency and also the possible side effects of using them. To counter the problem of fast mutation, scientists are working fast to study the genetic base of these viruses in order to learn how they mutate and what causes them to mutate and maybe get some answers to how they can counter this and produce a vaccine that will work for a longer time interval.

the answer is b. my dude

the difference of the poems of walt whitman and emily dickinson is that whitman uses personification, whereas dickinson avoids figurative language. whitman incorporates transcendentalism and realism in his works. on the other hand, dickinson's poems talks about death and immortality.