Omaha Steve's Labor Group

A small dose like you would get from someone passing in a store aisle is easy for most immune systems to eradicate, but if you spend a great amount of time with an infected person your body becomes overwhelmed.

I read that once it goes into the bloodstream there isn't much they can do. Your immune system has to defeat it before it gets to that point, which it will do in a healthy person and low dosage.