Mouse droppings are poisonous

If the mice have a lot to eat in winter and spring, cleaning up the gazebo can be a health risk. The rodents are among the most important hosts of the hantaviruses, which can be dangerous to humans. Infected animals excrete the pathogens in their saliva, urine and feces. If the infectious residue is whirled up with the dust when sweeping out huts, barns or cellar corners, the spring cleaner can become infected with the virus.

This season the supply situation for the mice seems to be pretty good, because the number of infections is higher than it has been for a long time. "This year could be a record year," says Detlev Krüger from the consulting laboratory for hantaviruses at the Charité in Berlin. In Baden-Württemberg alone, over 450 cases have been reported since the beginning of the year, far more than in the whole of Germany last year. By mid-May, 607 Hanta infections from all over Germany had been reported to the Robert Koch Institute (RKI). The number of infections fluctuates greatly from year to year. In 2016, the RKI registered 282 patients, in 2012 it was 2825 - the highest level to date. Krüger expects 2000 to 3000 cases nationwide by the end of the year.

One of the things to blame is the beech trees, which shed so abundant beechnuts last autumn that mice and other rodents were able to multiply thanks to the oversupply of food. In Germany it is mainly the bank vole that transmits the pathogen. But other rodents and shrews also serve as hosts for the viruses. The severity of the disease can vary depending on the type of pathogen. The hantavirus types circulating in Central Europe are rarely life-threatening, 90 percent of the infections would not even be noticed or be mistaken for other diseases, says Krüger.

With local hantaviruses, a more severe infection usually has a flu-like course at first, with a high fever for three to four days, plus headache, stomach and back pain. In rare cases, kidney failure occurs. Krüger estimates the death rate in Germany to be less than 0.1 percent, "because the virus types here are comparatively harmless and the medical care is so good". In Brazil, on the other hand, there are more dangerous types of virus, where the death rate among those infected is 50 percent. "It's a killer there," says Krüger.

In Germany there are a few regions with a significantly increased risk of Hanta. These include the Swabian Alb, the Osnabrück area, the Odenwald, Upper Swabia, the Franconian Alb and the Bavarian Forest. The reason why the Hanta load of the rodents fluctuates so strongly regionally is probably due to the animals' loyalty to their home. Bank voles, for example, prefer to stay in their valley, as genetic analyzes have shown.

In the affected regions, foresters and other people who work or exercise outdoors must therefore be particularly careful. And before sweeping out the basement, it may be advisable to moisten the dust a little so that it stays on the floor. Better still, make sure that mice don't get into the house in the first place.