Brad Erdahl was mostly just annoyed when he discovered a rodent had gotten into his bread supply while camping, never imagining the string of events that was about to unfold.

It happened in late June while Erdhal was staying in a camper at Goose Creek Campground near Leavenworth. Late one night, he awoke and turned on a light. He spotted a mouse nearby sitting on the floor.

“I got down, got a broom, and swept him out the front door,” Erdhal said. He cleaned the trailer of a few mouse droppings and wiped everything down.

After he arrived back home over the weekend in Everett, Erdhal began having flu-like symptoms: Muscle fatigue. Body aches. Fever.

The symptoms intensified over the next few days. A body temperature with rollercoaster-like readings, peaking at 103 degrees then dropping to 97.

By Monday, June 28, he began feeling faint and his vision was strangely affected. “I went outside on a bright, sunny day and it seemed like a snow white-out,” he said. “It hurt to keep my eyes open … I could hardly even walk.”

He called his doctor and she told him to go to an emergency room right away. His wife drove him to Evergreen Hospital Medical Center in Kirkland.

Still, Erdahl didn’t think he had anything serious until he saw the reaction of emergency room staff. “Typically they put you in there and you’re waiting a long time,” he said. “That wasn’t the case.”

Erdahl, 42, was in shock, had low blood pressure and a temperature of 103 degrees, and his kidneys were failing, said Dr. Francis Riedo, an infectious disease specialist who works at the hospital. Erdahl was transferred to the intensive care unit.

“He was breathing fast and short breaths,” his wife, Shelly Erdahl, said. He was diagnosed with pneumonia and put on a ventilator.

“They tested me for everything on the planet,” Erdahl said. “The infectious disease doctor was questioning my wife, ‘What’s he been doing?’ “

“She’s not thinking about the mouse,” Erdahl said. “Why would you?”

Nevertheless, the biggest clue to Erdahl’s illness would come from that late-night spotting of a mouse while he was camping.

It was a deer mouse, identified by its coat of blackish-brown fur with a large white underbelly, one of several types of mice in the United States known to carry hantavirus.

The virus begins with flu-like symptoms, just like Erdhal had.

Hantavirus is relatively rare, with only 503 cases documented in the United States since 1993, according to the Centers for Disease Control and Prevention. But more than a third — 36 percent — of those diagnosed with the disease die.

From four to 10 days after initial exposure, patients experience coughing and shortness of breath. The lungs fill with fluid.

The virus is spread when fresh urine, droppings or nesting materials are stirred up, such as by sweeping, according to the federal health agency. That allows the virus to get into the air and for it to be inhaled. Instead of vaccuuming or sweeping around where mice have been, health officials recommend cleaning up with water and bleach.

Among the symptoms that led physicians to suspect hantavirus was that Erdahl had been in good health until three days before he was hospitalized, he had been camping and he had kidney failure.

Tests confirmed their hunch, making Erdahl the first person to be diagnosed with the illness in Washington this year, according to the state Department of Health.

Erdahl was hospitalized for 13 days, 10 spent in the intensive care unit. Even after he left intensive care, the virus left him so weak it was hard for him to raise a piece of bread to his mouth, he said.

When Erdahl was discharged July 11, he was still easily fatigued. Yet just two weeks after leaving the hospital, he was at his job as a construction superintendent. He now rates his recovery at 90 percent, but has been told it could be a several more months before he feels fully back to normal.

Since learning of Erdahl’s case, the Wenatchee National Forest has posted signs on its campground bulletin boards warning of the potential for deer mice to spread hantavirus.

Even though Erdahl has camped since he was a boy, he said he had no idea that simply sweeping up after a mouse could nearly cost him his life.

Erdahl said he hopes that people will take extra care when spending time outdoors — and even at home — around places mice can find a way squirm into.

“I’ve camped and been around those environments all my life,” Erdahl said. “I never, ever would suspect that something like that could happen so easily.

“Just be alert and aware.”

How to avoid hantavirus

The Snohomish Health District recommends these steps to minimize your risk of hantavirus infection:

Air out cabins or shelters, check for signs of rodent infestation, and disinfect the cabins or shelters before sleeping in them.

Do not stir up dust by sweeping or vacuuming.

Before cleaning, spray the area wet with a mix of 1 ½ cups of bleach to a gallon of water. This disinfects and suppresses contaminated dust.

Once everything has soaked for 10 minutes, wear waterproof gloves and remove all of the nest material, trapped mice and droppings with a damp towel, then mop or sponge the area with the bleach solution.

Wipe the area clean while it is damp, rather than stirring up dust by vacuuming or sweeping. Plug rodent holes with steel wool.

Do not pitch your tent or put sleeping bags near rodent droppings or burrows, and avoid sleeping on the bare ground. Use tents with floors or bring a ground cloth.

Steam clean or shampoo upholstered furniture and carpets that show evidence of rodent exposure.

Spray dead rodents with disinfectant and then double-bag along with all cleaning materials. Clean your gloves with disinfectant or soap and water before taking them off. After taking off the clean gloves, wash your hands thoroughly with soap and water.

Keep all food and trash in rodent-proof containers. Never handle or feed wild rodents.

If you were exposed to rodents or rodent-infested buildings and have symptoms of fever, muscle aches, and severe shortness of breath, contact a medical clinic immediately.

Sharon Salyer: 425-339-3486 or salyer@heraldnet.com