Anyone who has got a pet rat at home knows how intelligent and adaptable these animals are. And they are becoming increasingly popular as pets. However, as with all animals in human care, there is a risk of them transmitting pathogens, such as hantaviruses, to humans.
Hantaviruses, which occur worldwide, belong to the group of rodent-borne pathogens that are transmissible to humans and are often underestimated. In Germany as well as in other parts of Europe, the number of infections increases regularly in years in which the rodent population is high.
The types of hantavirus occurring in Germany are transmitted by various mouse species. The mice usually show no symptoms, but they still excrete the virus in their saliva, faeces and urine. Humans can become infected by inhaling contaminated dust or soil particles, for example while gardening.
Seoul virus poses new threat
In southern and western Germany, bank voles are considered the main carriers of Puumala hantavirus. In north-eastern Germany, however, infections with Dobrava-Belgrade virus, mainly transmitted by striped field mice, are more common.
Sporadic cases of Seoul virus (SEOV) infection are also found throughout Europe and are considered very rare. SEOV is primarily transmitted through contact with rat excretions. In Germany, SEOV was first detected as the cause of a human hantavirus infection in November 2020. A young woman from Lower Saxony fell seriously ill and required intensive care treatment for acute kidney failure. The infection could be traced back to her pet rat, which was also found to be carrying the virus. This was the first documented case of autochthonous SEOV infection in Germany. Up to now, six cases of SEOV infection in humans have been reported in Germany, five of which were linked to pet rats. This highlights the importance of pets as potential carriers of the virus.1
A diagnostic challenge due to cross reactivity
The true number of SEOV infections may be underestimated. This is because the nucleocapsid proteins used in serological tests have highly similar amino acid sequences to those of other hantavirus species, which can lead to strong cross reactions. As part of an external quality assessment, this hypothesis was investigated by sending serum samples from a patient in Lower Saxony, taken two months after full recovery, to eight specialised European laboratories for examination. All of the laboratories performed serological tests to detect antibodies against various hantavirus species. The results revealed significant cross reactions of the samples with related hantavirus nucleocapsid proteins during both the initial screening for IgG and IgM and the subsequent confirmatory testing. This made correct serotyping impossible.1 A similar outcome was achieved in the quality assessment scheme “Virus Immunology – Hantaviruses” by INSTAND e.V. in September 2024. In this case, the sample was also taken from the aforementioned patient, but eight months after the onset of the disease.
Both analyses illustrate that an SEOV infection should always be considered when unexpected patterns emerge during serological diagnostics, such as a significant increase in antibody titers against Hantaan virus (HTNV) in the absence of a corresponding travel history or where is known contact with rats.
Table: Results of Euroimmun tests for both of the aforementioned patient samples
In most cases, hantavirus infections are not identified as such clinically. The infection typically presents as a sudden high fever lasting for three to four days, accompanied by non-specific flu-like symptoms such as headaches, muscle aches and chills. Complications may include kidney or lung failure, which can be fatal. In infections with the Puumala, Dobrava-Belgrade or Seoul viruses, kidney involvement is predominant.
Early diagnosis of the viral disease is crucial to avoid serious complications. This is usually based on the clinical picture and serological examinations. For the detection of specific anti-hantavirus antibodies (IgM and IgG), Euroimmun offers various enzyme-linked immunosorbent assays (ELISA) and immunofluorescence assays (IFA), as well as the corresponding automation solutions.
Visit our website for more information about suitable tests for hantavirus diagnostics: Emerging Diseases | Euroimmun
- Hofmann J, et al. Hantavirus Disease Cluster Caused by Seoul Virus, Germany. Emerg Infect Dis 30(1):133-135 (2024).
