The terrifying mouse-born hantavirus claimed the life of a third person on Thursday, while the total number of those infected has reached eight—but officials warn that up to 22,000 could have been exposed the disease. A global health alert has been issued since as many as 2,500 of those exposed could live outside the U.S. The camps remain open, on the recommendation of public-health inspectors. Though a park spokesman said "we try to keep the rodents out," he added that "it's impossible to say every tent cabin is rodent-proof. That's impossible." Hantavirus pulmonary syndrome has no cure, inhibits breathing, and has a 36 percent fatality rate.