I am a strong proponent of Probiotic use for general health. This particular brand is special in that it has no added carbohydrate fillers (dextrose, cellulose) that could feed the toxic bacteria or fungi I'm combating. As with all probiotics, the best results are seen from regular use because you never know when you'll encounter an airborne or food borne pathogen. I have not seen this or any other Probiotic formula have effect against an active virus, other than just keeping a healthy immune system