As flu season ramps up in the U.S., influenza is not as simple as it first appears, with several different strains in play.

Depending on what strain of influenza virus is circulating in a given year, the letters and numbers may indicate the risk of spreading beyond the usual prevalence of infection and expected ...

State and federal data show high levels of respiratory illnesses. Here's what to know about the illnesses circulating this ...

As China continues to monitor an increase in cases of human metapneumovirus (HMPV), here's what you need to know about the ...