Response to Gaynor Black

When/why did influenza become shortened to flu?

Dear Gaynor, you asked: 

Would you please write a brief summary of the main differences between the various groups of viruses, such as rhinovirus, coronavirus, etc. What exactly is influenza? How does influenza differ from influenza-like illnesses? When/why did influenza become shortened to flu? What is a cold? Just trying to follow the discussions and b…