Here is the "shooting" solution to the problem:
If the 10,000 Yosemite visitors start doing the Immunizer for 2 - 3 minutes a day, any hantavirus infection symptoms are excluded, because the dreaded virus would have been killed. The Immunizer is a simple exercise, but is The Complete Colds/Flus/AIDS/Yosemite/West Nile/Cancers Prevention - The Deadliest Virus Killer on Earth - normally done for a minute a day for kids and adults as the full prevention of the major plagues of civilization. No killer viruses on Earth got any chance against the tremendous power of the immunizer - they just die the moment they touch you...

Doing the immunizer I stay healthy all the time. For me Cold and Flu Season does not exist. I wear my summer tees and shorts all the time, even at air temperature of -15C...

Human body can be a fortress immune against viral attack...

I offer my Dream Immunizer (The Deadliest Virus Killer) to the world for 2 trillion US Dollars. The sooner I am paid, he better for the Entire World... I will disclose the greatest discovery in human history to everybody and all of us will stay absolutely healthy all the time, all our lives, even if we are directly exposed to any possibly existing viruses on Earth - mutant, deadly and all the like...