As with most viral infections, you were probably infected several days before you developed any symptoms and you were most infectious during that "incubation period." Help protect the baby now by continuing to breastfeed.
Since mothers and babies are in such close contact, chances are you have already passed the infection to the baby. But by providing the baby with immune factors in the milk, chances are the baby will not get sick but actually become immune. That's what we want, not to prevent his being exposed. But if the baby does get sick, chances are he will be less sick than if you don't breastfeed.
By the way, if you are well enough to type this question, you are well enough to have the baby at the breast.