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Health officials say Yosemite hantavirus outbreak unlikely to reach Oakland

on September 3, 2012

Late last month, officials from Yosemite National Park announced that two people who visited the park in June died later from hantavirus pulmonary syndrome (HPS), a dangerous disease spread through the urine, saliva or feces of infected rodents.

But there should be no serious concern for contracting hantavirus in Oakland, health officials say. Deer mice are the only known species to carry hantavirus in California, according to the California Department of Fish and Game website. Deer mice reside throughout North America in woodland or desert areas, not in urban settings.

“You can recognize a deer mouse because they are two-colored: they have a white belly and their backside is grey or brown, and they have large ears with no fur on them,” said Ralph Montano, a spokesman for the California Department of Public Health (CDPH), in a phone interview last week. “A house mouse is usually a solid color with smaller, furry ears.”

The virus is not contagious between humans. “Hantavirus is spread from one mouse to the next, but we don’t know the transmission rate,” said Norma Arceo, public information officer for the CDPH. “Roughly 14 percent of deer mice in California are infected.”

In urban and suburban areas, wild rodents are most often house mice or roof rats, both species that do not carry hantavirus, the CDPH website states. However, in any wilderness area or facility where feces or rodent nests are visible, residents should be aware of the symptoms of hantaviris and avoid contact with wild rodents anyway, as it may be hard to discern a deer mouse from the more common house mouse. For Oakland residents, this means taking precautionary measures like keeping food in tightly sealed containers, sealing holes where mice and other rodents could enter a home and disposing of dead rodents and feces using gloves and a bleach solution.

The symptoms of hantavirus consist of unusually high fevers, fatigue and muscle aches— similar to those of the more common influenza virus. “It’s a pretty rapid onset, and the death rate is about one third,” said Roger Baxter, an infectious disease expert at Kaiser Permanente’s Oakland Medical Center and co-director of the Kaiser Permanente Vaccine Study Center, in a phone interview last Wednesday. “That’s really high for a virus.”

Montano said symptoms commonly appear within one to two weeks of exposure. If left untreated, she said, hantavirus can quickly progress into the lungs, resulting in heart, lung or kidney failure.

“Antibiotics have no effect,” Arthur Reingold, professor and chair of the Division of Epidemiology at UC Berkeley’s School of Public Health, said in a phone interview. “It’s really what we call ‘supportive treatment,’ in terms of keeping you breathing and other organs working until your body recovers.”

Yosemite officials have said they believe the virus seems to have been contracted only by visitors who stayed in Curry Village, the tent cabin campground located in central Yosemite Valley beneath Glacier Point. They announced that as many as 1,700 visitors who stayed there from mid-June throughout the end of August might have been exposed.

According to a press release from the CDPH, six visitors are so far known to have become infected. Of those, two have died. Both victims—a visitor from Pennsylvania, and a 37-year-old man from Alameda County—stayed in the Boystown area of Curry Village. Officials from Yosemite shut down all visitor access to Boystown on August 28, the press release says.

Since hantavirus was discovered in 1993, there have been 60 reported cases in California. In the last decade, CDPH has tested nearly 7,000 mice statewide, Montano said. This year, there have been seven reported accounts of hantavirus in the state.

“If someone is having some of these early symptoms and they’ve recently been staying in a camping area where they know there were mice around, they should go to their doctor and make them aware of their recent stay so that they can make an assessment,” Montano said.

Sherri Willis, public information officer for the Alameda County Public Health Department, said in a phone interview that deer mice last tested positive for hantavirus in Alameda County in 1999 and 2000 in four locations: Del Valle Regional Park (1999), Ohlone Regional Wilderness (1999), Bethany Reservoir (1999) and Camp Parks (2000). According to CDPH’s website, the last time rodents in California were tested for hantavirus in Alameda County was in 2011, from June through December.

In rodent-infested spaces or in the wilderness, individuals are advised to ventilate the area for two hours and wear plastic gloves when cleaning, according to a press release from Yosemite National Park. Using a bleach solution, wearing a face mask and disposing of cleaning materials in a double plastic bag are also suggested practices.

“A classic example is that someone goes into a cabin in someplace like the Sierras that’s been closed off for the winter,” Reingold said. “They clean it up, they sweep up the dust, and there’s dried urine and feces that get into the air.”

Concern over contracting hantavirus should not outweigh venturing outdoors, Baxter said. Enclosed areas, like cabins, offer greater chances of becoming ill as they can accumulate dust with traces of urine, feces or saliva from infected rodents.

“It’s a nasty infection, but it is still really rare,” Baxter said. “We don’t think this is some sort of new epidemic.”


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