West Nile fever in Germany
How early career researchers calculate the mosquito season and the spread of viruses
Hamburg, World Mosquito Day, 20 August 2026: Researchers at the Bernhard Nocht Institute for Tropical Medicine (BNITM) are using a range of mathematical models to calculate the expected spread of West Nile virus in Germany. They are also developing forecasting models that predict how mosquito populations will develop and which surveillance and prevention measures hold the most promise.
West Nile virus is transmitted by mosquitoes. It circulates mainly between birds and mosquitoes and has been detected regularly in Germany since 2018. In recent years, the virus has spread increasingly northwards and westwards across Europe. Most infections in humans cause mild symptoms or go unnoticed. However, some people develop severe disease, including meningitis or encephalitis. Horses can also become seriously ill.
Spatial model of West Nile virus spread
Two scientists of the BMFTR-funded early-career research group Arbovirus Ecology have developed models to improve our understanding of how mosquitoes and the virus spread.
In a study published in the journal One Health, Pride Duve led the development of a spatially resolved mathematical model of West Nile virus spread in Germany between 2019 and 2025. The model combines temperature data for Germany with the movement patterns of migratory and resident birds and the biology of Culex mosquitoes, which transmit the virus.
The simulations reproduce known outbreak areas in eastern Germany. They also reveal a ‘spread corridor’ from the eastern federal states through parts of northern Germany to the south-west. In recent years, summer temperatures in these regions have favoured mosquito reproduction and virus development. Migratory birds probably carried the virus into new areas. Notably, the model maps not only established hotspots but also provides plausible explanations for isolated cases in regions that had previously been affected only rarely. In some areas, the model predicted an increased risk several years before the first cases were reported there.
‘Our model calculations show that West Nile cases in Germany do not occur at random. They follow a recurring spatial pattern. Temperature, migratory birds and local mosquito density jointly determine where cases are likely during a given season,’ says Pride Duve, a mathematician and the study’s first author at the Bernhard Nocht Institute for Tropical Medicine.
Where West Nile fever recurs and when the mosquito season poses the greatest risk
In another study, Leif Rauhöft and colleagues developed a process-based model of the life cycle of Culex mosquitoes, the main vectors of West Nile virus in Germany. The model describes mosquito development from eggs through larvae and pupae to adults under realistic temperature conditions. The researchers tested it against field data from Germany. It can predict with relative precision when mosquito activity will be particularly high in a region.
‘Public health authorities and veterinary professionals face a very practical question: When does the mosquito season begin in our region, and when do we need to be especially vigilant? Our model reproduces the development of the main West Nile vectors so well that we can predict the start and peak of the season with relative precision,’ says Leif Rauhöft, a doctoral researcher at the Bernhard Nocht Institute for Tropical Medicine.
Model output for a single sampling site in Hamburg, Germany, between 2020 and 2023, with corresponding environmental data (A), aquatic life stages (males and females summarised) (B) and adult life stages (nulliparous and parous females summarised; the Y-axis was square-root transformed for visualisation) (C).
Building on this work, Pride Duve and colleagues used a further model to test different strategies for controlling West Nile fever. The simulations included reducing mosquito populations by eliminating breeding sites, vaccinating horses in affected regions, and strengthening personal protection against mosquito bites, for example through insect repellents and clothing that covers the skin. The model calculates how different combinations of these measures change the number and course of outbreaks. A free web application allows users to test the model.
Towards an early warning system for West Nile fever
In future, these modelling approaches could contribute to a national or regional early warning system for West Nile fever. Such a system would regularly combine current climate data, findings from bird and horse surveillance, and information on mosquito populations. It would translate these data into risk maps. Authorities could then decide where to intensify surveillance, reduce breeding sites or launch information campaigns. The researchers stress that model calculations do not replace field surveillance. They complement it. Models help to structure unanswered questions and set priorities, including where additional data would be particularly valuable.
The studies also show how early-career researchers can use mathematical methods to make a practical contribution to understanding and controlling vector-borne diseases.
Background information
West Nile virus belongs to the Flaviviridae family and is transmitted mainly by mosquitoes of the genus Culex. Birds act as amplification hosts in which the virus can multiply to high levels. Mosquitoes acquire the virus when they feed on blood and can transmit it in subsequent bites.
Humans and horses are considered dead-end hosts. They can become ill but do not contribute to the virus’s onward transmission because the amount of virus in their blood is too low to infect other mosquitoes. Most human infections cause no symptoms or only mild flu-like symptoms. The actual number of cases is therefore probably higher than the number reported. A small proportion of people develop neuroinvasive disease, in which the virus attacks the central nervous system. This can cause meningitis, for example. In rare cases, the disease can be fatal.
West Nile virus was first detected in birds in eastern Germany in 2018. It has since become established in many German federal states. Cases in birds and horses occur mainly in summer and early autumn. Reports of locally acquired human infections are also increasing. Climate change is bringing longer and warmer summers. These conditions favour virus replication and help the virus spread.
Original publications
Pride Duve, Felix Gregor Sauer, Renke Lühken (2026): Modelling the impact of temperature and bird migration on the spread of West Nile virus. One Health, 22:101386, DOI: https://doi.org/10.1016/j.onehlt.2026.101386
Pride Duve, Felix Gregor Sauer, Renke Lühken (2026): Modelling the control of West Nile virus using mosquito reduction methods, equid vaccination, and human behavioural adoption of personal protective equipment. Ecological Modelling, 517: 111605 DOI: https://doi.org/10.1016/j.ecolmodel.2026.111605
Leif Rauhöft, Pride Duve, Sara M. Martins Afonso, Hanna Jöst, Tatiana Şuleşco, Felix G. Sauer, Renke Lühken (2026): A process-based model simulating the life cycle of Culex pipiens s.s./Cx. torrentium in Germany. Parasites & Vectors, 19:207, DOI: https://doi.org/10.1186/s13071-026-07410-4.
About the Bernhard Nocht Institute for Tropical Medicine (BNITM)
The Bernhard Nocht Institute for Tropical Medicine (BNITM) is Germany’s largest institution for research, healthcare and teaching in the field of tropical and emerging infectious diseases. The BNITM’s research priorities have always been viewed through the lens of global health and the ‘One Health’ approach, as well as from the perspective of translation – the transfer of basic research into practical application. This research approach is also reflected in the Institute’s five sections: Pathogen -> Interface (immunology, host/pathogen) -> Patient (clinical) -> Population (epidemiology) -> Implementation (successful application of knowledge). A Data Science Centre has also been newly established.
Current research priorities include malaria, haemorrhagic fever viruses, neglected tropical diseases (NTDs), immunology, epidemiology and the clinical aspects of tropical infections, as well as the mechanisms of viral transmission by mosquitoes. For handling highly pathogenic viruses and infected insects, the Institute has laboratories of the highest biosafety level (BSL-4) and a biosafety insectarium (BSL-3). The BNITM’s mobile laboratories are on standby for global outbreak response involving highly pathogenic or highly infectious viruses.
The BNITM is the National Reference Centre for Tropical Pathogens, a Consultation Laboratory for BornaViruses, a WHO Collaborating Centre for Arboviruses and Haemorrhagic Fever Viruses, a WHO Collaborating Centre for Behavioural Research in Global Health (BRIGHT), and a member institute of the Leibniz Association.
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Contact person
Dr Renke Lühken
Leader of the BMFTR-Early Career Research Group Arbovirus Ecology, RG Vector Control
Phone : +49 40 285380-862
Email : luehken@bnitm.de
Julia Rauner
Public Relations
Phone : +49 40 285380-264
Email : presse@bnitm.de
Further information
- Duve et al.: Modelling the impact of temperature and bird migration on the spread of West Nile virus
- Duve et al.: Modelling the control of West Nile virus using mosquito reduction methods, equid vaccination, and human behavioural adoption of personal protective equipment
- Rauhöft et al.: A process-based model simulating the life-cycle of Culex pipiens s.s./Cx. torrentium (Diptera: Culicidae) in Germany
- Test the model here
