 [ Symptoms ] does caffeine cause heart disease [ Disease ] most helpful answer that would be difficult to accurately determine since some people can harbor strep for years i would assume that your son was more contagious within a day of his symptoms strep can be passed on to others for about a day after an appropriate treatment has started not all people are susceptible to getting strep easily since our immune system does a good job fighting it off your other children have just as much chance of getting it from someone else at school than from a sibling make sure your son with the strep does not share a drinkglass and change his toothbrush to a new one if the toothbrushes are thrown into a drawer where they can touch other toothbrushes this is a good way to pass it on