Everyone around my office has been sick for weeks. Even my boss who hasn't taken a minute of sick time for two years was off for two days.
Whatever it is, it's nasty and seems to travel all over the body. Good rule of thumb is your temperature. High temp normally means a virus which can only be handled with rest, fluids and probably increased Vitamin C. A low temp for more than 24 hours is usually an indicator that it's bacterial and you'd need antibiotics. Caution - taking those leftover antibiotics from your medicine cabinet is a very bad idea.
Yes, I did work in health care for 5 years in another life.