There are lots of people every year that are infected. The difference between them and those of us who get infected are the immune system. The healthy immune system can fight the virus. These folks may feel bad for a day or so and then they are better. We who are infected have a weak immune system. The virus is not prejudice. If the person has a special blood type, they eat you up as they love it. Also has something to do with the carbon dioxide you breath out that they like.