Normally you'll be fine 12-24 hours later though sometimes it can last longer if you have a weak immune system and get a secondary infection. Drink lots of water (or some other liquid with no sugar or calories in it) and try to rest. The no sugar thing is key as if there are any of the bad bacteria left then they can feed on the sugar to grow and reproduce. I'd try to fast for a day as well though a multivitamin can't hurt as long as it doesn't contain sugar.