The 1918 influenza virus swept the globe ... that has "pandemic potential." These photos show the devastation of a pandemic, and how the Spanish flu brought the world to its knees not so long ...

Avian influenza A (H5N1) has mutated, so the symptoms of bird flu could change as more people get sick in 2025.

"The Chinese poultry lineage may have experienced more vaccine-driven selection compared to other lineages," the researchers wrote.