Toothbrushes may contain bacteria. However, they don't make you sick. This is because your immune system is strong enough to fight against those bacteria. They may also be contaminated with the bacteria from your oral cavity especially if you had an active infection or disease affecting your mouth in any way. You can continue using the same toothbrush after the disease as your immune system now knows how to fight against that organism. However, if you share it with someone else it is likely to make them sick.