My whole family has this bug that causes sore throat, coughing, weak and sore muscles, yellow phlegm, tiredness, basically cold symptoms....but the crazy thing is, after 3-4 days it goes away for a few days, THEN COMES BACK.

This has been going on for about 3 weeks now, and I've ran into quite a few people recently who have the SAME EXACT THING.

Any ideas what is causing this? I'm 30 and never had this before.