Have you ever wondered why you have to get a flu shot every year, but some vaccines are one-and-done? It all has to do with how and how fast viruses evolve - and that depends on mutation rates.

A 13-year-old girl in British Columbia who was hospitalized with bird flu for several weeks late last year harbored a mutated version of the virus, according to a report published this week in the New ...

But watching how the flu virus sneaks into cells has been difficult because standard microscopes can't capture these fast, tiny steps clearly. In a breakthrough study, scientists from Switzerland and ...