Hantavirus infections

People can get infected with hantaviruses upon contact with rodents such as rats or mice and their droppings. People can also get infected with the viruses from dust that has been stirred up. This sometimes happens, for example, when cleaning a dusty shed or attic. The disease is similar to the flu, but often also damages the kidneys. Severe forms of the disease are rare, but can be fatal. 

In Germany, the prevalence of the disease varies from year to year. It depends how many rodents there are that can transmit the pathogen. In the last eight years the illnesses reported by health authorities and state offices were between 161 and 2,823 per year. Hygiene rules and avoiding contact help to protect people from being infected and therefore from the illness. 

80 to 85 percent of people with hantavirus infections do not have any symptoms or only have mild ones.  

Typical symptoms are fever for three to four days with back, head and limb pain. The symptoms occur about two to four weeks after a person is infected. Depending on the virus type, the infection can be more serious and then damage kidneys or lungs in particular. 

If the following symptoms occur, it can indicate a hantavirus infection:

• sudden onset of fever of over 38.5 degrees Celsius
• back, head and limb pain
• foamy or bloody urine
• elevated kidney values, especially creatinine
• elevated protein in urine
• fewer platelets (thrombocytes) in the blood
• urine output that is first reduced, later increased

There are various hantaviruses that cause a similar set of symptoms. They occur all over the world. It is mainly rats, but also other small mammals that carry the hantavirus infection to humans. 

In Germany, there are the following potentially disease-causing hantaviruses:

Puumala virus

Puumala viruses are the most common in Germany and mainly occur in the south and west. The bank vole is the host animal and carrier. In the last few years, there have been outbreaks of the disease mainly in the following regions: the Swabian Jura and the Franconian Jura, Upper Swabia, Bavarian Forest, Spessart, Lower Franconia, Odenwald, northeast Hesse, Teutoburg Forest, western Thuringia, Osnabrück and Münsterland region.

Dobrava-Belgrade virus 

Dobrava-Belgrade viruses mainly occur in the north and south of Germany. The striped field mouse native to the northern and eastern regions of Germany is the host animal and carrier. 

Seoul virus

Bred and wild rats harbor these viruses. The first cases were found in 2019 in Lower Saxony.

Tula virus

Field mice, found all over Germany, are the carriers of tula viruses. The first confirmed infection was discovered in 2019 in Germany. But as there is no regular test for tula viruses, the number of infections is believed to be much higher.

Hantaviruses persist in mice and rats and other small mammals. These host animals excrete the viruses through their saliva, urine and feces that stay infectious for several days as a result. People usually get infected by breathing in pathogen-containing dust, or from this dust getting into skin wounds. It can also be transmitted through bites or contaminated food. 

People who perform the following activities are particularly at risk: garden work, forestry and agricultural work, especially when cleaning sheds and stables where there are rodents.

But people can also get infected with hantaviruses when engaging in activities outdoors such as jogging, hunting or camping. These also include military personnel who take part in outdoor exercises.

Hantaviruses are common all over the world. The more host animals there are, the more often the disease occurs. If rodents such as bank voles have a good supply of food, they can proliferate. Accordingly, the amount of virus-contaminated mouse excrement in the environment also increases, making the hantaviruses spread more rapidly and increasing disease. The amount of rainfall per year also plays a role. High rainfall leads for example to a “mast year” – a bumper crop of beechnuts or acorns – the following year, which increases the number of animals.

Since food supply and rainfall fluctuate over the years, the number of disease cases also fluctuates. This means that in Germany in 2018 there were only about 230 cases of the disease reported, while in 2019 it was just over 1,500.  

The virus types that occur in Germany are very rarely serious and mainly cause flu-like symptoms and impair kidney function. This is known as hemorrhagic fever with renal syndrome (nephropathia epidemica). It can take several weeks or months to clear up, but leaves no lasting complications. 

There are also two serious forms that can be fatal:

Hemorrhagic fever with renal syndrome

The illness starts in the same way as an uncomplicated hantavirus infection. But a few days later, the following symptoms develop:

• severe stomach and back pain
• diarrhea and vomiting
• dizziness and drop in blood pressure and, later, shock
• bleeding in the conjunctiva and skin
• impaired kidney function and, later, kidney failure

In 5 to 15 percent of cases, however, the infection is fatal. The hemorrhagic fever with renal syndrome that is caused by the virus types in Germany is usually milder with no bleeding or shock. Mortality is below one percent.

Hantavirus-induced cardiopulmonary syndrome

The illness begins suddenly with fever, nausea and vomiting, a feeling of weakness, stomach and limb pain. The following symptoms occur 4 to 10 days later:

• cough and shortness of breath
• rapid heartbeat

The lung symptoms can quickly get worse and lead to acute respiratory syndrome. This form has a fatal outcome in 25 to 40 percent of those who become ill.

There is no vaccine available in Europe yet. You can only prevent an infection by avoiding being infected and avoiding contact with rodents and their droppings. Wash your hands and hair thoroughly after being in basements, attics or sheds. Wear a face mask when working in rooms potentially contaminated with mice excrement and, once you have finished work, wash your work clothes at 60 degrees Celsius.

You can also undertake other effective measures.

These are ways in which you can prevent a mice infestation:

• Keep food securely and tightly closed, for example in cupboards and plastic and metal containers.
• Do not leave animal food and water out overnight.
• Dispose of waste in sealable dustbins and garbage cans.
• Do not put any leftover food or animal waste in the compost.
• Eliminate nesting opportunities for rodents, i.e. rubbish dumps, bulky waste and used tires.

This is what you can do in the fight against mice and rats:

• Put down mouse and rat traps in dark corners and along the walls.
• Make sure you keep traps out of the reach of children and pets.
• Check the traps regularly.
• Consult a professional pest controller if necessary.

This is how you get rid of dead mice or their droppings:

• Put gloves and a face mask on.
• Place dead mice into a plastic bag, seal it, and put it in the household waste.
• Before cleaning, ventilate the rooms where there has been a mice infestation for 30 minutes.
• Stop dust from being swirled up by wetting surfaces before cleaning.
• Do not use a vacuum cleaner as the blower spreads viruses in the air.
• Clean all contaminated surfaces with household detergent.
• Once you have finished cleaning, wash your hands and hair, have a shower and wash your work clothes.

You can find more information about this topic in the “Information on how to avoid hantavirus infections” leaflet from the Robert Koch Institute (in German).

If doctors think someone might have an infection with hantaviruses, they take their blood to have the laboratory determine whether there are antibodies against the virus. The virus itself can only be detected in the blood for a short time in the early stages of the illness.

There is no special medication that directly targets the hantaviruses. Antipyretic (fever-reducing) pain medication such as paracetamol can relieve the symptoms. If the infection is severe, patients come to the intensive care unit. Sometimes they also have to be put on a ventilator.