Every year we have between 40 and 80 cases, with about three...

Every year we have between 40 and 80 cases, with about three of these clusters. No one really knows why, nor does anyone really know why this virus attacked this age group (of young people in their late teens or early 20s). We do know it is spread through close contact by oral secretions. About five percent of the population has the virus all the time and never gets sick, but is always contagious. We don't know why.