Breaking down the difference between a cold and influenza

DEAR DR. ROACH: What is the difference between a cold and the flu? -- A.T.R.ANSWER: Both colds and influenza (the “flu”) are respiratory illnesses that are caused by viruses. Influenza is caused specifically by the influenza viruses, which come in two main types (A and B). Influenza A is further broken down into different subtypes based on hemaggluti...