* National park's hantavirus toll rises to six, with two
* Most victims believed infected while staying in tent
* Deer mice that carry disease found nesting between walls
SAN FRANCISCO, Aug 30 (Reuters) - Two more visitors to
Yosemite National Park have been diagnosed with a deadly
rodent-borne virus, raising the total number of people infected
in the unusual outbreak to six, California public health
officials said Thursday.
Two men died from the rare lung disease called hantavirus
pulmonary syndrome, and four other people survived the
rodent-borne illness. Most of the victims are believed to have
contracted the virus while staying in tent-style cabins this
summer in a popular camping area called Curry Village.
Park officials earlier this week shut down 91 insulated
tent-cabins after finding deer mice, which carry the disease and
can burrow through pencil-sized holes, nesting between the
double walls of the structures.
Park authorities have notified 2,900 parties of visitors who
rented the tent cabins from June through August that they may
have been exposed to hantavirus.
Four who were infected at Yosemite this summer slept in the
insulated tent cabins. One slept elsewhere in Curry Village,
located in a valley beneath the iconic Half Dome rock formation,
and the sixth case remains under investigation.
One man from northern California and another from
Pennsylvania died. Three of the victims have recovered, and one
remains hospitalized, the state Department of Public Health said
in a press release.
Experts continued to investigate the outbreak, and the
number of cases could rise as visitors who were exposed to the
virus but have not yet shown symptoms fall ill, the agency said.
Nearly 4 million people visit Yosemite each year, attracted
to the park's dramatic scenery and hiking trails. Roughly 70
percent of those visitors congregate in Yosemite Valley, where
Curry Village is located.
Hantavirus is carried in rodent feces, urine and saliva that
dries out and mixes with dust that can be inhaled by humans,
especially in small, confined spaces with poor ventilation.
People also can be infected by eating contaminated food,
touching contaminated surfaces or being bitten by infected
STARTS WITH FLU-LIKE SYMPTOMS
The virus starts out causing flu-like symptoms, including
headache, fever, muscle ache, shortness of breath and cough.
Initial symptoms may appear up to six weeks after exposure and
can lead to severe breathing difficulties and death.
Although there is no cure for hantavirus, treatment after
early detection through blood tests can save lives. The virus,
which has never been known to be transmitted between humans,
kills 38 percent of those it infects.
"The earlier it's caught and supportive care is given, the
better the survival rate," said Dr. Vicki Kramer, chief of
ve c t or-borne diseases at the state Public Health Department.
Dr. Charles Chiu, an infectious disease specialist at the
University of California, San Francisco, said he made a habit of
airing out his tent-cabin before occupying it as a precaution
against possible virus-carrying dust particles when he stayed in
Curry Village a few years ago.
But even Chiu said he was surprised to learn that a
hantavirus had killed two people and stricken others who slept
in the same structures this summer.
"It wasn't something even I had thought of at the time,"
Chiu, who studies hantavirus, told Reuters.
Hantavirus previously infected two Yosemite visitors, one in
2000 and another in 2010, but at higher elevations.
Melanie Norall of Palo Alto, California, is monitoring her
8-year-old daughter's every sniffle. They stayed in a cabin
outside Yosemite's north entrance at the end of July and awoke
to mice scurrying and eating nuts out of their luggage.
The vast majority of hantavirus victims are young and
middle-age adults, Chiu said, probably because they are mostly
likely to engage in activities that would readily expose them,
such as chopping and carrying fire wood or sweeping the floors.
"The message should not be you should stop camping. The
important thing is general awareness of this disease and to
avoid wild rodents in general," Chiu said.
Since it was first recognized in 1993, hantavirus pulmonary
syndrome has been diagnosed in 64 people in California.
Nationwide, the virus sickened 587 people between 1993 and 2011,
according to government data.
(Editing by Steve Gorman)