A third person has died from the rare, rodent-carried Hantavirus after visiting Yosemite National Park, bringing the total number of infected persons to eight and prompting warnings that the virus is not contained to just one area of the park, health officials said.
The latest victim hailed from West Virginia, according to the Kanawha-Charleston Health Department in West Virginia.
Since June, eight park visitors, including six from California, have contracted the virus, according to Yosemite officials. Three of those infections have been fatal.
Park officials have warned thousands of Yosemite campers who stayed in the "Signature Tents" at Curry Village between mid-June and the end of August that they are at risk of contracting Hantavirus pulmonary syndrome (HPS), which is spread by contact with infected rodents, primarily deer mice, according to the Centers for Disease Control (CDC).
But on Thursday, it was revealed that the virus is not confined to Curry Village, according to a statement from the park.
One of the infected campers, who exhibited mild symptoms and is recovering, stayed in multiple High Sierra Camps in Yosemite in July.
The five High Sierra Camps are similar to the Curry Village tent cabins, but they're spaced about 6 to 10 miles apart and are accessible only via backpacking trails at higher elevation than Yosemite Valley.
The other seven cases have all been connected to the historic Curry Village tent cabins, which were recently been closed to the public.
It can take up to six weeks for symptoms of the virus to show, though they usually appear 2 to 4 weeks after exposure. Early stage symptoms include fatigue, fever and body aches, and can rapidly progress to severe difficulty breathing.
While there is no cure for Hantavirus, oxygen treatment can increase the chance of survival for infected persons in severe respiratory distress and early detection is key, said Lola Russell, CDC spokeswoman.
The latest outbreak has prompted international warning calls and emails to about 1,700 park visitors.
Hantavirus was first thrust into the public's awareness in 1993, when the virus was identified during an outbreak in the southwestern U.S.
CDC officials say the 1993 outbreak – which infected 42 people from 12 states – is the most comparable incident to the current outbreak.
Health officials at the time scrambled to figure out what was making people sick, and though great strides have been made in the study of the virus, there are still many questions that surround it, said Craig Manning, with the Viral Special Pathogens Branch of the CDC.
"There was higher than normal rainfall during the summer of 1993 and that led to a dramatic increase in the population of deer mice, which resulted in more opportunities for humans to be exposed to the virus," Manning said.
Since 1993, there have been 60 cases in California and 602 cases nationally, Manning said, describing the infections as "quite rare."
About one-third of California cases have been fatal, in line with the virus’ fatality rate which hovers at around 36 percent.
Manning said the recent outbreak has caused people to worry that a house- or field mouse may pose a threat to them.
“The virus is very specific as to its preference for hosts,” he said, adding that deer mice can be distinguished by their reddish-brown fur and white underbelly, and are smaller than field mice.
The deer mouse is one of four rodents which can carry the virus found in every state in the U.S. The white-footed mouse, cotton rat and rice rat can also host Hantavirus.
Deer mice are the most common carriers on the virus, and about 12 percent of their population is positive for Hantavirus.
CDPH officials issued the following advice for those going to wilderness areas where mice area present:
More information is available at the CDC website's page on the hantavirus.