At this time of year many people take advantage of the sunny weather to have a good clear out. Sitting outside in the sun we are quickly reminded that the outbuildings or shed hasn’t been cleaned out for many months, perhaps years. Alternatively if the sun is extremely strong you may find yourself drawn inside to the nice cool cellar which may also require a seasonal sort out.

If you are considering these tasks it is worth considering the dangers which may be lurking in those dark, untouched corners. If there is any chance that mice or even rats have made their home in your outbuildings, cellar or garage the area could be a highly contagious source of Hantavirus. This is a microbe which appears to be relatively harmless for its rodents hosts but in some parts of the world it is potentially fatal for humans.

Hantaviruses are a relatively recently discovered group of pathogens which first gained notoriety during the Korean War when over 3000 US troops became infected. The mortality rate of this Korean Hemorrhagic Fever (now referred to as ‘Hemorrhagic Fever with Renal Syndrome’ or HFRS) was estimated to be 5-10%. It took another 25 years of research to identify the Hantavirus as the causative agent. The virus was named after the Hantan River in South Korea where it was first isolated in the late 1970s by a research group led by Ho-Wang Lee. Although the virus has only recently been identified the disease itself is not new; it was reported in Chinese medical records more than 1000 years ago.

In more recent times the virus was one of a dozen or so pathogens which were included in the now suspended US biological weapons programme (I have recently written another article on the debate about scientific experimentation with serious pathogens. This can be found here).

In addition to HFRS the Hantavirus can also cause Hantavirus Pulmonary Syndrome (HPS). Whereas with HFRS the main effect is in the blood vessels the most pronounced symptom of HPS is associated with the lungs. This is also a very serious disease; in its website the Washington State Department of Health estimates that about one in three people diagnosed with HPS have died. When it was first identified in the southwest of the USA HPS was called Four Corners Disease. It is now found throughout the States and although the disease is relatively rare its fatality rate is approximately 60%.

The reason my attention was drawn to these diseases is that so far this year the number of Hantavirus infections occurring in Germany have reached record levels. The Robert-Koch Institute has identified 2070 cases to date in 2012. This compares with only 305 cases registered in the whole of 2011. Since 2001 all cases of infection with Hantaviruses in Germany must be registered with the medical authorities.

The normal host for the virus in Germany is the Bank Vole (Rötelmaus in German or Myodes glareolus). Generally the Bank Vole lives in woodland, hedgerows and other dense vegetation such as bracken and brambles and is found in Western Europe (including the UK) and northern Asia. Like other rodents Bank Voles are often attracted indoors where they can find shelter, warmth and a ready supply of food. Cellars, garages, outbuildings and sheds are therefore obvious targets.

Hantaviruses spread to humans when their normal rodent hosts shed the virus in their urine, droppings and saliva. Transmission normally occurs when people breathe in air contaminated with the virus. This can happen when a person disturbs an area containing these rodent ‘products’. Sweeping out an infested area or a rodent nest will cause the virus to become airborne and the risk of inhalation increases considerably. In addition bites from rodents can also lead to Hantavirus disease. Another way of becoming infected is by touching an area contaminated with rodent urine, saliva or droppings and then touching your mouth or nose. It is also thought that eating food contaminated with these rodent products can lead to the illness.

Fortunately the symptoms seen so far in Germany are mild compared with those of the US and Korean outbreaks. Typical symptoms are back ache, a rapidly worsening flu-like fever and sometimes traces of blood in the urine. However the fact that the number of cases has increased dramatically is a worrying trend.

In the US Hantavirus infections have been due to human contact with areas frequented by deer mice, cotton rats, rice rats or white footed mice. As it does not appear to cause a serious illness in its rodent host it is quite normal for the virus to exist in a significant percentage of the animals in the wild. For example when 1,100 Deer Mice were tested in Washington about 14% were infected with a Hantavirus (in this case the Sin Nobre Hantavirus).

As I have a number of US visitors who regularly visit my website I have included below some guidelines from the Washington State Department of Health to help readers prevent contamination by these very dangerous rodent borne diseases. This approach should also be considered in other parts of the World, like Germany and the UK, to limit the risk of infection from their less fatal (so far at least) local forms of the disease.

How can you prevent Hantavirus infections?

Keep rodents out of your home and workplace. Always take precautions when cleaning, sealing and trapping rodent-infested areas.

Seal up cracks and gaps in buildings including window and door sills, under sinks around the pipes, in foundations, attics and any rodent entry hole.

Trap indoor rats and mice with snap traps.

Remove rodent food sources. Keep food (including pet food) in rodent proof containers.

Clean up rodent infested areas:

• Wear rubber, latex, vinyl or nitrile gloves.
• Do not stir up dust by vacuuming, sweeping, or any other means.
• Thoroughly wet contaminated areas including trapped mice, droppings, and nests with a 10% hypochlorite (bleach) solution: Mix 1½ cups of household bleach in 1 gallon of water (or 1 part bleach to 9 parts water). Once everything is soaked for 10 minutes, remove all of the nest material, mice or droppings with damp towel and then mop or sponge the area with bleach solution.
• Steam clean or shampoo upholstered furniture and carpets with evidence of rodent exposure.
• Spray dead rodents with disinfectant and then double-bag along with all cleaning materials. Bury, burn, or throw out rodent in appropriate waste disposal system.
• Disinfect gloves with disinfectant or soap and water before taking them off.
• After taking off the clean gloves, thoroughly wash hands with soap and water (or use a waterless alcohol-based hand rub when soap is not available).

What precautions should you use when working, hiking, or camping outdoors?

• Avoid coming into contact with rodents and rodent burrows or disturbing dens.
• Air out cabins and shelters, then check for signs of rodent infestation. Do not sweep out infested cabins. Instead, use the guidelines above for disinfecting cabins or shelters before sleeping in them.
• Do not pitch tents or place sleeping bags near rodent droppings or burrows.
• If possible, do not sleep on the bare ground. Use tents with floors or a ground cloth.
• Keep food in rodent-proof containers!
• Handle trash according to site restrictions and keep it in rodent proof containers until disposed of.
• Do not handle or feed wild rodents.

What should you do if you think you have been exposed to mouse droppings?

If you have been exposed to rodents or rodent infested buildings and have symptoms of fever, muscle aches, and severe shortness of breath, see your health care provider immediately. Inform your health care provider of possible rodent exposure so that he/she is alerted to the possibility of rodent-borne diseases, such as Hantavirus Pulmonary Syndrome.

If you are interested in finding out more information about these diseases please take a look at the Washington State Department of Health’s website. This can be found here.

In addition the Centre for Disease Control and Prevention (CDC) also has a lot of useful information including a brochure “Facts About Hantavirus” which can be downloaded from the site in PDF format. This Website can be found here.

Happy cleaning!

Chris Duggleby