LOS ANGELES -- National Park Service officials and public health authorities are considering notifying visitors from other countries about a recent outbreak of hantavirus at Yosemite National Park that has killed two people and sickened at least one other.
Earlier this week, park officials emailed some 1,700 visitors who stayed in the "signature tent cabins" in Yosemite's Curry Village between mid-June and late August, said park spokesman Scott Gediman. Letters were sent to visitors whose email addresses were not on record.
Dr. David Wong, an epidemiologist with the National Park Service's Office of Public Health, said Wednesday that officials were still trying to determine how many of those 1,700 visitors were from out of the country.
If that number is a "sizable population," he said, officials would consider asking the World Health Organization to help broaden the warning beyond the U.S.
Officials were also working with the U.S. Centers for Disease Control and Prevention to issue an alert through the nationwide "health advisory network," which notifies health care providers -- not just government health departments, which Wong said were notified Sunday night. Wong said he hoped the second alert would go out Wednesday.
"The notification is our No. 1 priority," Wong said. "We don't want to just rely on email for that ... we want to come up with other strategies to make sure that people hear about this."
All four stayed separately at the signature tent cabins in Curry Village in June, Gediman said. Officials have traced the outbreak to deer mouse droppings in the area.
Repeated cases of hantavirus at the same location within a year is "very rare," said Dr. Barbara Knust, an epidemiologist with the CDC. There have been 587 cases of human infection from hantavirus recorded between 1993 -- when the virus was first identified in the Four Corners area -- and 2011, according to the CDC. About one-third have been fatal.
Jana McCabe, a Yosemite park ranger, called the outbreak "unprecedented."
"We take this extremely seriously," she said. "We want to know what's going on."
Transmitted through urine, droppings or saliva of infected rodents, hantavirus pulmonary syndrome takes between one and six weeks to manifest itself in humans, officials said. The symptoms -- fatigue, fever, muscle aches, nausea, vomiting and abdominal pain -- are often confused with the flu, Knust said, but can quickly worsen as the infected person's lungs begin to fill with fluid.
Hantavirus exposures have been traced to Yosemite twice before, in 2000 and 2010, McCabe said. Neither case, linked to lodging in Tuolumne Meadows, was fatal.