Four more cases of hantavirus have been reported among people who
visited Yosemite National Park in California, bringing the total number
of cases to six, the California Department of Public Health said
Thursday. Two of the six people infected have died.
MORE: Yosemite warns visitors about hantavirus
The health department is
"working closely with the National Park Service and the Centers for
Disease Control and Prevention to further investigate the cluster of
Hantavirus Pulmonary Syndrome cases in Yosemite and reduce the risk of
other visitors becoming ill from this virus," said Dr. Ron Chapman,
health department director.
MORE: 2nd Yosemite visitor dies of rodent-borne illness
Those infected visited
the park between early June and mid-July, the health department said.
Most stayed at the park's popular Curry Village "tent cabins." Yosemite
closed the tent cabins indefinitely on Tuesday.
The park sent letters to
around 1,700 summer visitors on Monday and Tuesday, explaining that
hantavirus cases had been uncovered and that visitors should see their
doctors if symptoms surface, park spokesman Scott Gediman said.
Hantavirus pulmonary
syndrome is a rare lung disease that kills about a third of those who
get infected. Symptoms can include fever, muscle aches and fatigue,
though it is not communicable from person to person.
"However, if the
individual is experiencing fever and fatigue, and has a history of
potential rural rodent exposure, together with shortness of breath,
(that) would be strongly suggestive of HPS," the U.S. Centers for
Disease Control and Prevention said.
In September 2010, the
Tuolumne Meadows Lodge at Yosemite was assessed for hantavirus risk by
the health department and received a rating of "high risk" for
hantavirus activity. The evaluator made a number of recommendations to
decrease the risk. CNN was unable to determine what, if any, action the
park took on the recommendations. The lodge is not in the same area of
the park as Curry Village.
In the United States, the carriers of hantavirus are deer mice, cotton rats, rice rats and white-footed mice.
The virus can be present
in the rodents' urine, droppings and saliva, and it is spread to people
when they breathe in air contaminated with the virus, the CDC says.
Don Neubacher,
Yosemite's superintendent, said that people typically don't fall ill
with hantavirus until between one and six weeks after they are exposed.
"The health of our
visitors is our paramount concern, and we are making every effort to
notify and inform our visitors of any potential illness," Neubacher
said.
Officials have focused
on deer mice, common in the high-elevation eastern Sierra Nevada region.
The mice are gray or brown on top, with white bellies. Their ears have
no fur.
"Rodents can infest a
whole range of these structures," said Dr. Vicki Kramer, chief of the
health department's vector-borne disease section. "Deer mice can get in a
hole one-quarter inch in diameter."
In addition to cleaning
the 400 camp structures, park officials have said they have increased
routine measures to reduce the hantavirus risk.
"You cannot eliminate
all the mice," Kramer said. "There are a lot of people and snacks that
people bring into their tents or cabins."
Before this year, Yosemite National Park saw one hantavirus case each in 2000 and 2010.
There is no specific
treatment for a hantavirus infection, according to the CDC, but the
earlier a patient is brought to intensive care, the better.
CNN