Levels of influenza nationwide are now at the highest they have been since the peak of the 2009 swine flu pandemic, according ...

Here’s what to know about the flu viruses. Influenza A viruses come in many varieties. Four subtypes commonly affect humans, Dr. Lowen said — you may have heard of H1N1, for example.

Partial CDC data suggest that influenza deaths may have already reached as high as 2% of deaths for the week ending on Feb. 1 ...

For the first time since 1952, publication of the CDC's Morbidity and Mortality Weekly Report was halted. It returned on Feb.

Hilleman knew that it was just a matter of time before the influenza virus shifted and caused a pandemic similar to the one in 1918. Exactly when that shift would occur was anyone’s guess.