Key symptom: Fever that comes on fast

Best fix: Acetaminophen or ibuprofen

If your fever hits 101°F or 102°F and comes with chest discomfort plus major aches and exhaustion, it’s probably the seasonal flu, says Neil Schachter MD, author of The Good Doctor’s Guide to Colds and Flu. Take pain pills for fever and aches, rest, and drink lots of liquids. Those at high risk—pregnant, elderly, or chronically ill—may need antiviral meds such as Tamiflu or Relenza.