Colds and flus are both contagious respiratory illnesses caused by viruses that surge seasonally — typically when the weather drives people indoors. Strep throat is also a highly contagious illness, but it’s caused by bacteria instead of a virus.

Because there are a lot of overlapping symptoms, it can be hard to know whether you have a cold, the flu, or strep. With strep throat, the main symptoms are fever and a sore throat. Colds tend to be confined to upper respiratory symptoms (coughs, congestion, running nose, sneezing, sore throat). Symptoms tend to come on gradually, and fevers (if there are any) are mild.

By contrast, flu symptoms tend to come on fast, and are more likely to be accompanied by a higher fever. Flus aren’t necessarily limited to upper respiratory symptoms. They can also include debilitating headaches, body aches, and fatigue. Sometimes people will experience GI symptoms with the flu (nausea, vomiting, or diarrhea).

If you suspect you have the flu or strep, it’s wise to get tested. Ask your pharmacist if they offer testing for the flu or strep. If you do have the flu, treating it within 48 hours of the onset of symptoms can reduce the duration and severity of symptoms. If you have strep throat, antibiotic treatment is necessary — both to help you feel better and also to prevent rare but serious complications (like rheumatic fever). For the common cold, ask your pharmacist about over-the-counter treatments that can help.