Wednesday, June 25, 2014

Hantaviruses: Of Mice And Men

Striped field mouse (Apodemus agrarius)


# 8780



While relatively rare, one of the infectious diseases that we tend to hear more about during the summer months is Hantavirus, mostly because during the summer people are more likely to come in contact with mice, and their leavings.  


Overnight, the Canadian Press carried the following report on a recent fatal case in Saskatchewan.


Saskatchewan adult dies from hantavirus; health officials urge caution

REGINA — The Canadian Press

Published Tuesday, Jun. 24 2014, 7:51 PM EDT

Health officials in Saskatchewan say an adult from the southern part of the province is dead after contracting hantavirus.

Hantavirus infection is rare and is transmitted by breathing in airborne particles from the droppings, urine and saliva of infected deer mice.

Exposure can happen when people are camping, opening their cottage, getting an RV or boat ready for the season, moving woodpiles or cleaning out buildings.

“We know that this person had cleaned out an outdoor building. I actually don’t know whether it was a garage or a cabin ... and it was a building that was likely to have had an opportunity to be infested with mice,” Denise Werker, Saskatchewan’s deputy chief medical health officer, said Tuesday.

No details were released about the age or gender of the person who died.

Werker said the death underscores the message that everyone should be careful.

(Continue . . . )

You may recall that in the fall of 2012, we followed an outbreak at Yosemite National Park (see MMWR: Yosemite Hantavirus) which resulted in 10 infections, and 3 deaths. 


Hantaviruses’ are a collective term for a group of viruses carried by various types of  rodents - that vary in distribution, symptomology, and severity around the world.


While in North America, the `Sin Nombre’  virus typically causes a severe form of pneumonia called HPS (Hantavirus Pulmonary Syndrome) and is fatal in about 30% of time, in Europe the Puumala virus, which is carried by the bank vole (Myodes glareolus), is rarely fatal (<1%) in humans.


As you can see by the CDC map below, Hantavirus infections in the United States are most common west of the Mississippi, although the total reported over the past 21 years is less than 640 cases.



Although first detected in soldiers during the Korean War (see Hantavirus: An Emerging Infectious Disease), Hantavirus was first identified in the United States in the early 1990s. For a fascinating look at that epidemiological investigation, you may wish to visit: 


Tracking a Mystery Disease:
The Detailed Story of Hantavirus Pulmonary Syndrome


While the odds of contracting Hantavirus are slim -given the high mortality rate - it is well worth heeding the following advice from public health agencies. Canada’s Occupational Safety & Health Agency CCOHS, recommends:


What occupations are at risk?

Cases of Hantavirus infection contracted in Canada and the United States have been associated with these activities:

  • Sweeping out a barn and other ranch buildings
  • Trapping and studying mice
  • Using compressed air and dry sweeping to clean up wood waste in a sawmill
  • Handling grain contaminated with mouse droppings and urine
  • Entering a barn infested with mice
  • Planting or harvesting field crops
  • Occupying previously vacant dwellings
  • Disturbing rodent-infested areas while hiking or camping
  • Living in dwellings with a sizable indoor rodent population

For workers that might be exposed to rodents as part of their normal job duties, employers are required to comply with relevant occupational health and safety regulations in their jurisdiction. Typically, employers are required to develop and implement an exposure control plan to eliminate or reduce the risk and hazard of Hantavirus in their workplace.

How can we prevent exposure to Hantavirus?

There are no vaccines against Hantavirus. Since human infection occurs through inhalation of contaminated material, clean-up procedures must be performed in a way that limits the amount of airborne dust. Treat all mice and droppings as being potentially infected. People involved in clean-up activities where there are not heavy accumulation of droppings should wear disposable protective clothing and gloves (neoprene, nitrile or latex-free), rubber boots and a disposable N95 respirator. For cleaning up rodent contaminated areas with heavy accumulations of droppings it is necessary to use powered air-purifying (PARP) or air-supplied respirators with P100 filters and eye or face protection to avoid contact with any aerosols.

Dead mice, nests and droppings should be soaked thoroughly with a 1:10 solution of sodium hypochlorite (household bleach). Bleach kills the virus and reduces the chance of further transmission. The contaminated material should be placed in a plastic bag and sealed for disposal. Disinfect by wet-wiping all reusable respirator surfaces, gloves, rubber boots and goggles with bleach solution. All disposable protective clothing, gloves and respirators should be placed in plastic bags and sealed for disposal. Please contact your local environmental authorities concerning approved disposal methods.

Thoroughly wash hands with soap and water after removing the gloves.

For more information on how you can prevent rodent infestations, the following information is available on the CDC Rodents site. And for more information, the CDC offers a 16 page PDF  on Hantavirus, which is available on their Hantavirus Main page.


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