The Killer that Comes on Tiny Feet

By Nicole Johnston
Tuesday July 11, 2000.

With the summer season in full swing, many urbanites are fleeing the city for cottage retreats or a chance to commune with nature while camping or hiking.

Whether your rural experiences are limited to occasional visits, or you live or work year-round in rural environs, you could face the threat of a potentially deadly virus called hantavirus.

But by taking certain precautions, you can protect yourself from the risk of exposure.

For Charlie Coleman, a farmer from the rural area of McAuley, Man., and his family, the warnings have come too late. The death of their son's common-law wife, Patricia Killmury, was an unforeseen tragedy that he wants to make certain no other family goes through.

In July of last year, the 27-year-old woman was the first person in Manitoba known to have contracted the deadly virus that, until then, had claimed lives only in British Columbia and Alberta.

She was moving to Brandon to start a hair-dressing course and may have been going through storage items that brought her into contact with hantavirus-infected mouse droppings, Mr. Coleman said.

Ms. Killmury began to feel ill on a Thursday, complaining of flu-like symptoms. Bouts of dizziness led her doctor to suspect an inner-ear infection. But by Sunday, she was clinging to life. She died the next day.

And in late May of this year, the virus killed another victim, this time a 68-year-old Manitoba woman - the province's second victim.

The illness, known as hantavirus pulmonary syndrome (HPS), causes its victim's lungs to fill with fluid, leading to respiratory failure - the insidious hallmark of this disease. Fluid buildup in the lungs is thought to be the immune system's response to the virus, rather than the effect of the virus itself. The patients can drown in their own fluids.

The virus makes its way into humans through the infected feces, urine and salvia of the ubiquitous deer mouse, Peromyscus maniculatus. The dried excreta turns to dust and, when stirred up, enables the virus to become airborne and inhaled.

In the United States, other rodents can spread the hantavirus, but the deer mouse is the only known carrier in Canada. The deceptively cute rodent has large ears, large eyes, a white belly, a tail with white sides and can be found in a variety of colours ranging from grey to reddish brown, depending on its age.

To date, 34 people in the western provinces have been diagnosed since testing began in Canada in 1994. So far, 13 have died. In the United States, about 250 people are known to have been infected since the first outbreak was described in New Mexico in 1993.

The disease often proves fatal partly because there aren't any drugs to halt it. Clinical trails of an antiviral remedy called ribavirin have been disappointing.

Harvey Artsob, chief of zoonotic diseases and special pathogens with Health Canada in Winnipeg, believes HPS has been present here for a long time. "We've probably had hundreds or even thousands of cases over the centuries," he said.

What is new about the disease is the ability to detect it, according to Tom Ksiazek, chief of the diseases-assessment section of the special pathogens branch at the Centers for Disease Control and Prevention (CDC) in Atlanta.

Scientists suspect that the weather changes brought about by El Nino in 1992-1993 allowed the deer-mouse population to flourish, resulting in the first noticeable outbreak in New Mexico in 1993.

The illness is often detected only as it becomes more severe, Dr. Ksiazek said. "This is a very serious illness that requires the best sort of critical care…The severe form of the disease comes very rapidly, and if patients can be supported (in an acute-care facility), they often recover very quickly after going through this phase."

The critical stage, Dr. Artsob added, seems to be when people begin having difficulty breathing. Patients and physicians should suspect hantavirus when there is a history of rodent exposure.

Six thousand rodents have been screened for hantavirus to date in Canada, and infected mice have been found in every province expect Prince Edward Island and Nova Scotia. But only limited numbers of mice were obtained in those areas, Dr. Artsob cautioned. And while the virus has been identified in Yukon, it hasn't been found in the Northwest Territories or Nunavut. At some sampling sites, as many as three out of ten deer mice have been found to be infected, but the prevalence rates can vary dramatically from area to area.

Any exposure to infected deer-mouse droppings can put you at risk. Although deer mice prefer woodland areas, they can find their way into cities.

So, whether you live in rural or urban areas, the best thing to do is to be on the safe side and take protective measures it you come across any rodent droppings or dead rodents.

One potentially risky activity is opening up and cleaning buildings that have been closed for the season, such as cottages, cabins, barns, garages and storage facilities. To start, open the windows and let the room air out for a few hours before cleaning.

And if you see signs of rodent infestation, or a dead rodent itself, Dr. Artsob says don't sweep or vacuum because this could stir up dust and allow the virus to become airborne.

Instead, disinfect the area with a bleach solution (one part bleach to nine parts water), or other strong household disinfectant such as Lysol, for at least 10 minutes.

Once everything is thoroughly wet with the bleach solution or disinfectant, clean up the contaminated material with a towel, and then mop or sponge the area with a disinfectant solution again.

"Disinfect the whole area, and not just where you see droppings," Dr. Artsob said. Also use gloves.

Any dead rodents should also be sprayed with disinfectant. Materials should be doubled-bagged and buried or burned. Gloves should also be disinfected before bring removed, and once degloved hands should be washed thoroughly with soap and water.

Mr. Coleman advises farmers to be particularly vigilant, because deer mice are a familiar presence on farms and like to make their homes in tractors, grain trucks and the air-conditioning systems on combines, which can mean rodent waste blowing straight at you. He warns farmers to shut off all equipment before investigating for rodent infestation and to always be cautious in storage sheds and other closed quarters.

The CDC recommends various measures to keep rodents at a safe distance. To prevent rodent infestation indoors, keep your home clean, especially the kitchen. Keep a tight-fit-ting lid on your garbage and don't leave food (including pet food) lying around in open containers. Seal potential entry holes. Spring-loaded traps can be put around baseboards, and environmentally approved poisons can be used, but use caution, because they can poison pets and humans, too.

To prevent infestation outdoors, clear grass and junk from around house foundations so mice won't build nests there. Keep woodpiles and garbage at least 30 meters or more away from the house.

For campers and hikers, air out and then disinfect shelters before using them. If possible do not sleep on the bare ground; use tents with floors or a ground cloth. (For better protection, use a cot with the sleeping surface at least 12 inches above the ground.) And keep food and water in tightly sealed containers.

"We advise everyone to take precautions in Canada," Dr. Artsob said.

But despite the potential threat of hantavirus, there's still no reason to curb summer outings.

As Dr. Artsob put it: "Son't get overly scared about it… Use common sense and don't overreact."

Signs and Symptoms of HPS

Many of the early symptoms of hantavirus pulmonary syndrome can mimic the flu and make early diagnosis difficult, says Elise Weiss, regional medical officer of health for southwestern Manitoba.

Anyone can be afflicted by the illness, although it is less common among children. Symptoms often begin to appear one to two weeks after exposure to infected mice droppings, but can take up to six weeks to appear.

Early symptoms include fever, headache, muscle aches and pain, dizziness, chills, nausea, vomiting, diarrhea and abdominal pain (experienced by approximately half of HPS patients).

The late symptoms begin to appear anywhere from a few to 10 days after the early symptoms, and include coughing and shortness of breath.

"That's the actual… respiratory distress syndrome progressing, "Dr. Weiss says. "The lungs are filling up with fluid." As a result, the patient begins drowning in his or her own fluid, and becomes deprived of oxygen.

There is no virus-specific treatment for HPS, and no vaccine. Treatment for HPS is supportive, meaning that the symptoms are dealt with as soon as they appear, ideally in a well-equipped intensive-care facility.

The actual diagnosis is made using a blood test that detects hantavirus antibodies. Other laboratory measures may also point to HPS. Usually, a clinical diagnosis is mode based on symptoms before the laboratory diagnosis is confirmed.

Sometimes these findings only begin to appear as the illness progresses.

Doctors and patients should suspect HPS when flu-like symptoms develop after a recent history of rodent exposure. "This is the index of suspicion, particularly with the respiratory picture," Dr. Weiss says. The onset of breathing difficulties often marks the critical stage.

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