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.

Amid the push to get the COVID-19 vaccine to many as possible to stem the pandemic, a new variant of the coronavirus that exploded in Brazil and has since been reported in the U.S. is causing concern ...

A variant strain of the coronavirus, one that was first discovered in the United Kingdom, is now the dominant strain of the virus circulating throughout the United States, CDC Director Rochelle ...

Bird flu has always worried pandemic planners, but a new twist is raising the stakes: scientists are now tracking variants that can keep multiplying even when a human body turns up the heat. A strain ...

At least 14 states and Washington, DC, are reporting high or very high flu activity. The dominant flu strain, a version of influenza A (H3N2) called subclade K, has multiple mutations that make it ...

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 ...