In the past decade there have been a number of outbreaks of West Nile Virus in Europe. Little is known of the transmission of this virus in the region, so it is uncertain whether these episodes are part of an erratic pattern of transmission or evidence of a change in long-term prevalence. Our knowledge about the natural history of the virus and its vectors in Europe has to be improved to assess the potential for transmission in European ecosystems.

The objectives are to understand area-wide past West Nile Virus (WNV) transmission patterns and related environmental events through the analysis of historical time series of climate and environmental data for observed WNV foci throughout Europe, and for "similar"; areas outside such foci, in WNV-outbreak and non-outbreak years and use the obtained outputs to assess the public health significance of WNV.

1. To use a landscape epidemiological approach to describe vector/host habitats where West Nile Virus transmission has been documented.

2. To clarify epidemiological events in the transmission of WNV in the 7 pilot field sites:

• To evaluate the annual WNV seroprevalence and incidence of WNV infection in horses.
• To identify WNV reservoirs through testing migrant and resident birds for WNV antibodies.
• To identify potential WNV vectors (mosquitoes) using host-baited traps.
• To determine the role of other ectoparasites of resident and migrant birds in WNV transmission and dissemination through the implementation of ectoparasite sampling protocols.
• To determine whether WNV is able to over-winter in Europe in hibernating adult Culex pipiens in urban ecosystems in Bucharest.

3. To clarify seasonal bird population variations and migration patterns in the Rhône delta.

4. To integrate information gathered through historical time series analysis and high resolution epidemiological studies in order to construct area-wide statistical models for the occurrence of WNV in Europe, from which to derive public/veterinary health recommendations.