Our 15 mth old came down with a virus - how likely is it that our 3 mth old will get it?

We wash our hands CONSTANTLY but the 15mth old just had the worst virus I've seen in a long time. Trouble breathing, grumpy, congested, the poor guy was in really rough shape. It started Monday - My 3 mth old is still feeding, and has had a runny nose, but do you think he's past the contagious stage? Because Noah's breathing was affected I just wondered if the antibodies in milk would be enough coupled with clean hands and changed cloths (at least 3 times a day) would be sufficient to keep Aiden from getting the virus. (The doc said Noah would be sick anywhere from 10 to 14 days, and that there was a good chance it could turn into bronchitis - He is finally feeling better today though...)