Prior exposure to one strain of influenza virus may weaken children's ability to mount an effective antibody response against their subsequent exposure to a different flu strain, according to a study ...

Add Yahoo as a preferred source to see more of our stories on Google. Respiratory virus season is in full swing across California, with several illnesses spreading across the state. Cases of influenza ...

This story was updated to add new information. A new flu variant is sweeping across the United States, causing millions of reported cases and doubling the number of hospitalizations in a surge doctors ...