Two cases of the rare hantavirus have been confirmed in King County, including one fatality, raising questions about when health officials should notify the public about such a low-risk, but dangerous threat.

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Maureen Waterbury came close to dying after she contracted a rare disease, hantavirus, in November. Waterbury, a registered nurse who lives in the Union Hill area outside Redmond, spent 10 days in intensive care and six on a ventilator, before recovering.

An Issaquah man, 34, was not so fortunate. He died Feb. 24 of hantavirus, according to King County health officials. But they did not notify the public of his death or of Waterbury’s case.

That led her husband, Mark Waterbury, to create a blog that has focused on two questions: Why was it taking King County so long to notify the public about the hantavirus cases? And, is it a hot spot for the respiratory disease, carried by particular rodents, that is deadly in 36 percent of reported cases?

The answer to the first is that notice is coming, Dr. Jeff Duchin, health officer for Public Health – Seattle & King County, said Monday.

“I agree it’s important to make the public aware,” Duchin said.

Tuesday afternoon, the agency issued a news release.

But there’s also some concern about unduly alarming the public about two cases of a rare disease that mostly appears in rural areas. “We do have to strike a balance because it’s a very rare disease,” Duchin said.

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Health officials didn’t finish investigating the second case, believed to have been caused by a mouse infestation in the Issaquah man’s house, until March 10, Duchin said. Meanwhile, his communicable-diseases staff has been busy dealing with a mumps outbreak, tuberculosis investigations and most recently, measles.

“In general, we’d strive to be more timely and get (public notice) up more quickly. But we have to prioritize,” Duchin said.

Only five cases of hantavirus have been diagnosed in King County in the past 20 years, according to state records. Fewer than three cases a year, on average, are reported in the state, most of them east of the Cascades. The disease is most often contracted by breathing mouse droppings stirred up by cleaning or some other activity.

The question of whether King County is a hantavirus hot spot is complicated.

Duchin knows a bit about hantavirus. As an epidemiologist for the Centers for Disease Control and Prevention (CDC), Duchin went to New Mexico in 1993 to try to figure out what was killing members of the Navajo Nation. The CDC concluded it was a new form of hantavirus transmitted by deer-mouse droppings.

Duchin wrote “one of the classic epidemiological papers” about the disease, said Dr. Barbara Knust, with the CDC’s Viral Special Pathogens Branch.

“I do think two cases separated by a few months is unusual for us,” Duchin said. “Only time will tell” if the two cases are a coincidence or a cluster. The two cases in King County deserve public attention, he said, but, “It’s not like it’s an emergency.”

The deer mouse, prevalent in much of North America, is the most common carrier of hantavirus. The “deceptively cute animal,” as the CDC puts it, lives in woodlands and deserts and is not found in urban areas, said Knust, an epidemiologist and veterinarian.

In his blog, Waterbury theorizes weather and environment may have created a situation in which food for deer mice is abundant, predators are fewer and the mouse population is booming.

Duchin called Waterbury’s theory “reasonable.” Public-health officials will be reaching out to wildlife experts for more information about the deer-mouse habitat, he said.

Hantavirus Pulmonary Syndrome (HPS) is the severe respiratory disease in humans caused by infection with hantavirus. Anyone who comes into contact with rodents that carry hantavirus is at risk, according to the CDC.

Rodent infestation in and around the home remains the primary risk for hantavirus exposure. There are no reported cases of hantavirus in the U.S. in which the disease was transmitted from one person to another, according to the CDC.

The mean age of the 659 confirmed cases in the U.S. since 1993 is 38 years old, according to the CDC. The infected have been relatively young, Knust said, because the disease is frequently found in people “doing active things like cleaning out cabins or going camping where they come in contact with rodents.”

Duchin said it’s not clear how Waterbury contracted hantavirus. Her husband’s theory is that deer mice had invaded her car and when she ran the heat or air conditioning with windows rolled up, she breathed particulates of mouse excrement.

Mark Waterbury doesn’t doubt that Duchin and his staff have been busy. He’s both frustrated and relieved that they now aim to notify the public of the local hantavirus cases.

“I’m pleased that it finally seems to be happening. But I’m confused as to why something like (his blog) is necessary,” he said.

“My whole thing is people should know about it so they can be more careful,” Maureen Waterbury said.