My friend had an illness about 3 weeks ago, treated with antibiotics. Symptoms included fever up to 102, moderate body/muscle aches, red rash across small of back, and heavy fatigue. It lasted a couple of weeks, then he felt much better and perkier. Rash almost disappeared. Now suddenlyi it s all back again. Current temperature is only 99, but he fears it s starting to climb. Possible causes????