U.S. officials had sounded a worldwide alert earlier this week, saying that up to 10,000 people were thought to be at risk of contracting hantavirus pulmonary syndrome after staying at the popular Curry Village camping area between June and August.

Yosemite spokesman Scott Gediman said the park was now expanding the warning to include another 12,000 people who stayed, or were still registered to stay, in the more remote High Sierra Camps, an area where visitors had not previously been considered to be at risk.

"We continue to try to be transparent, get the word out to everybody," Gediman said. "Early medical detection is incredibly important, and our goal right now is to reach out to people.

"If anybody is feeling any symptoms, we urge them to seek immediate medical attention."

Yosemite announced the expanded warning as it confirmed that a third park visitor had died of the disease and that the number of U.S. visitors to the park in California sickened by the virus had risen to eight.

One of those was a man who stayed in the High Sierra camps this summer and was diagnosed with a mild case of hantavirus pulmonary syndrome, Gediman said. The other seven U.S. visitors fell ill after staying in double-walled tent cabins in the Curry Village campground, located in a lower-elevation area of the park.

Health officials in France were also investigating two suspected hantavirus cases there of people who may have been exposed while at Yosemite.

Gediman identified the third fatality as a West Virginia resident who contracted hantavirus while staying in Curry Village tent cabins in June. That victim, whose gender was being kept confidential at the request of family, died at the end of July, and laboratory tests on Thursday confirmed the death was due to hantavirus, he said.

The World Health Organization also issued a global alert this week over the cases of hantavirus linked to Yosemite, and advised travelers to avoid exposure to rodents. Officials are concerned that more Yosemite visitors could develop the lung disease in the next month or so.

There is no cure for the disease, which kills over a third of those infected, but early detection through blood tests greatly increases survival rates. 

Related:

• US officials sound worldwide alert of Yosemite hantavirus risk