You may have come across this piece of advice: throw away your toothbrush after you have a cold, herpes, strep throat, or ear infection, because germs on the toothbrush can reinfect you and make you sick again. Some sources argue that this is false because after a viral infection we develop immunity through antibodies.  How do we make sense of this? Here are a few facts. Once used, toothbrushes harbor large numbers of bacteria and viruses, that increase in number with repeated use, and are also seen in larger numbers if there is fraying of the bristles. Toothbrushes stored in a container, or with a cap, as opposed to drying in air freely, harbor more bacteria and viruses. Herpes simplex viruses have been shown to remain live (able to replicate) on a toothbrush for up to 24 hours. Currently it is recommended to change your toothbrush every 3 months. Therefore as well, it is prudent in our opinion to discard or disinfect your toothbrush with mouthwash, better Listerine or best antiseptic mouthwash (chlorhexidine aka Peridex) after an infection. Also, never share a toothbrush and disinfect your toothbrush and any surfaces where virus containing droplets might have fallen if you have been sick. Best wishes — ProDentalFx, LLC (Sources: Int. Journal of STD & AIDS; Nursing Res. And Practice)