Nightly News | September 07, 2012
>>> federal officials have now expanded a worldwide alert to all those who have vacationed at yosemite national park this summer due to an outbreak of the deadly hantavirus, an illness spread to people by mice. and now 29,000 summertime visitors are being warned about the risk of illness. our report tonight from nbc's janet shamlian .
>> reporter: a ticket to yosemite comes with a warning.
>> there is information about hantavirus in here.
>> reporter: amid the vast granite cliffs and breathtaking waterfalls, the deadly hantavirus is also here. eight confirmed cases in the park. three people have died. because yosemite draws so many tourists from outside the u.s., the world health organization issued a global alert about the rare rodent-borne virus.
>> someone told us do you know there is a virus in yosemite park. we say oh, yes, we're going to there in a couple of days.
>> reporter: the popular curry village has been the epicenter of the outbreak. rangers believe mice got into the inner walls of some of the area's tent cabins. until now, all the cases have been tied to a single location here on the valley floor. now with a confirmed case in a different part of the park, there is concerned the danger zone could be much wider. health officials say as many as 29,000 people who visited the park could be at risk, almost triple their assessment of 10,000 just days ago.
>> the letter and e-mail that we're sending them is a health alert saying that we have had these cases, there is no need for, you know, immediate action unless people are exhibiting symptoms.
>> reporter: the early symptoms of hantavirus mimic the flu -- headaches, fever, and body ache. but the deadly virus cannot be transmitted from one person to another.
>> of course i'm concerned. i don't want to get a virus that's going to kill you.
>> reporter: he didn't cancel his trip, but others have. hard to get reservations made a year in advance have become no-shows as caution canceled many vacation. janet shamlian , nbc news, yosemite national park .