If you were prescribed antibiotics, then the culprit is bacteria not a virus. You must continue to take the antibiotics until gone, or the remaining bacteria will reproduce, making you sick again, and they will have developed a bit of a resistance to the antibiotics making them harder to treat in future.

Your body will tell you how hard you will be able to train. I would be surprised if you could get back to 5/6 hours the first few days back at it.