Have to agree with Singer on his perspective of keeping your immune system in top shape. Sure doesn't hurt to sanitize things you know a lot of people are touching and, of course your hands occasionally. Exercise (particularly cardio), adequate sleep and gut health all aid tremendously in staying healthy and free of illness. Probably 90% of all times I've ever been sick there is usually a precipitating factor that has diminished my immune system. It could be something as simple as forgetting to take a jacket when you really needed one all day.