it takes a month or a month and a half to present with symptoms. this is one of the things where who knows who you got it from and you do not present for a month and a half, it is frightening. >>guest: it is frightening. if people leave the national parks, particularly yellowstone and become sick, they should tell their doctor they have been had and they could have been supposed to hantavirus. >>trace: now we are reading there are 1,600 cases of west mile and 66 people have died. it surprises me but you are saying the numbers do not surprise you. why? >>guest: well, west nile is always a surprise because it is a new virus in this hemisphere. it is complex ecosystem. the virus is in the birds, it gets in the mosquitoes and the mosquitoes boat us. the interaction of the birds and mosquitoes determine how much west nile we are going do have and in what parts of the country. the drought may have made it