Hantavirus infections

People can get infected with hantaviruses upon contact with rodents such as rats or mice and their excretions. The virus can also be caught from dust that has been stirred up if it contains dried animal excretions. This can happen when cleaning out a dusty shed or loft, for example. 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 10 years, the number of cases reported by health authorities and state offices were between 143 and 1,747 per year. Hygiene rules and avoiding contact with rodents help to protect people from catching an infection and becoming ill. 

In many cases, there are very few or no symptoms following infection with a hantavirus. 

Typical symptoms are fever for three to four days with back, head and limb pain. The symptoms generally 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 the 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 and shivering
• headache and pain in the back and limbs
• foamy or bloody urine
• elevated kidney values, especially creatinine
• elevated protein in the urine
• fewer platelets (thrombocytes) in the blood in the first few days following infection
• urine output that is initially reduced and then increased

Hantaviruses persist in mice and rats and in other small mammals. These host animals excrete hantaviruses in their feces, urine, and saliva. Depending on environmental factors, such as air temperature, humidity, and sunshine, the viruses can remain in these excretions for up to 6 weeks. 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. 

Which pathogens cause a hantavirus infection?

Hantaviruses occur all over the world. There are various hantaviruses that cause a similar set of symptoms. Each type of virus prefers a different host animal. This means that some hantavirus infections only occur in regions where these host animals are native. The most important hantaviruses in Germany are the Puumala virus and the Dobrava-Belgrade virus. An overview of hantaviruses that can potentially cause disease is provided below: 

Puumala virus

Over 90 percent of all hantavirus infections in Germany are caused by the Puumala virus. This virus is particularly prevalent in the north-west, west, and south of Germany. The bank vole is the host animal and carrier. 

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

This virus occurs in both bred and wild rats. In Germany, several infections with this virus have been described. Most cases are suspected to occur in settings where people keep or breed rats. 

Tula virus

Tula viruses are transmitted by field mice, which are found in all parts of Germany. The first confirmed infection in Germany was in 2019. However, as there is no regular test for Tula viruses, the number of infections is believed to be much higher than recorded.

Hantaviruses don’t occur with the same frequency in all parts of Germany. That’s because the individual host animals are native to various regions.

Within the relevant regions, the following activities in particular are associated with a risk of infection: 

• Working in forestry and agriculture
• Spending time in, and especially cleaning, sheds and stalls where rodents are found
• Outdoor activities involving potential contact with rodents, such as gardening, camping, jogging, or hunting

The number of Hantavirus infections varies from year to year. The more host animals there are in a year, 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 excretions in the environment also increases, making the hantaviruses spread more rapidly and increasing disease. The food supply for host animals is influenced, for example, by the volume of rainfall in the previous year.

In Germany in 2022, for example, only about 140 cases of the disease were reported, while this number was just over 1,700 in 2021.

The virus types that occur in Germany are very rarely serious and in many cases, there are very few or no symptoms following infection.  

A hantavirus infection can take one of two different forms, which partially overlap with one another:

Hemorrhagic fever with renal syndrome (HFRS)

Kidney dysfunction is typical of this form of the disease.
In Germany, most cases are mild with flu-like symptoms (referred to as “nephropathia epidemica”). In these mild cases, the symptoms may persist for several weeks or months but people generally make a complete recovery. Mortality is well below one percent.

Severe forms of HFRS begin like a simple hantavirus infection. In the first few days after contracting the virus, typical symptoms include: 

• high fever and shivering
• headache
• severe stomach and back pain
• nausea and vomiting
• dizziness, light-headedness, and visual impairments
• in some cases, bleeding in the conjunctiva (the clear membrane covering the white of the eye) and skin

The disease enters a second phase after about a week. This usually starts with a drop in blood pressure, which can lead to shock in extreme cases. Impaired kidney function
and even kidney failure are typical.

This severe form of the disease causes death in 5 to 15 percent of cases. 

Hantavirus-induced cardiopulmonary syndrome

The illness begins suddenly with fever, nausea and vomiting, a feeling of weakness, stomach and limb pain. Coughing and shortness of breath develop 4 to 10 days later. These symptoms may deteriorate rapidly and lead to acute respiratory distress syndrome. This form has a fatal outcome in 25 to 40 percent of those who become ill.

No vaccine is available in Europe at present. You can prevent illness by avoiding being infected through contact with rodents and their excretions. When cleaning lofts, basements, or sheds or if you stir up dust when performing other activities such as moving large objects around, be sure to wash your hands and hair thoroughly afterwards. 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 take other effective measures: 

Ways to prevent a mouse 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.

How to get rid of 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.

How to get rid of dead mice and their excretions:

• 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 mouse 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 a hantavirus, they take their blood to have the laboratory determine whether there are antibodies against the virus. These antibodies cannot be detected in the blood until about 2 to 3 weeks following infection with 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 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. In some cases, they may require artificial ventilation or dialysis.