The flu virus is changing in ways never seen before, increasing infections and raising concerns about vaccine effectiveness and public health risks.

New versions of the H5N1 virus are increasingly adept at spreading. Suggestions to either let it rip in poultry or vaccinate the birds could backfire.

Flu viruses that can use a second cellular entry point may move more effectively between animals and humans, scientists say.

In the United States, flu shots are updated annually to include multiple types of influenza A and B viruses; scientists pick strains of the viruses expected to be dominant that year.

Experts and the Centers for Disease Control and Prevention agree that current risk to the general public is low. But flu viruses evolve, and it won’t take too many leaps for H5N1 bird flu to ...

Two types of influenza viruses are responsible for seasonal flu outbreaks: Influenza A and B. Influenza A accounts for around 75 percent of all cases and tends to cause more severe illness in adults.

Here is what you need to know about the bird flu: What is the bird flu and how is it spread? Avian influenza viruses occur naturally among wild aquatic birds such as ducks, geese, gulls, swans and ...

Here’s a look at the four major viruses that could ruin your holiday fun, or what the Brits are calling a “quad-demic,” which could stress emergency rooms this winter.

Flu viruses package essential functions into a small integral membrane protein known as M2. Such small membrane proteins represent major challenges for structural biology. A new study presented in ...

California researchers say the world may be just one genetic tweak away from human-to-human transmission of the H5N1 bird flu virus — a worrisome mutation that could open the door to widespread ...

Scientists have an idea of how bird flu would have to evolve in order to spread more easily among humans: A mutation in one protein on the virus' surface could help it bind better human cells.