West Nile Virus Poses Emerging Public Health Threat in Europe; Climate Change Blamed for Spatial Expansion of Pathogen

Over recent years, anthropogenic climate change has had unprecedented impacts on the global functions and services of ecosystems. There is mounting evidence that alterations in biodiversity redistribution due to climate change can impoverish human health.

(Photo: Wikimedia Commons/ Fabrizio Montarsi)

It is, therefore, essential to understand how human activities modulate large-scale public health concerns. Anthropogenic stressors can force changes in the distribution of species that transmit pathogens, like mosquitoes and ticks.

Emerging Mosquito-Borne Viruses in Europe

Mosquito-borne diseases, like malaria, dengue, and West Nile fever, involve complex ecological interactions that depend on local environmental conditions. Environmental changes can influence their causal pathogens' range, transmission rates, distribution, and seasonality.

West Nile virus (WNV) is one of the most widespread mosquito-borne viruses that hastily emerged in Europe. It is maintained in a bird-mosquito transmission cycle, with the species Culex pipienbeingas being the continent's most common and competent vector.

Mosquitoes get infected after biting an infectious bid and then become infectious themselves with the ability to transmit the virus through subsequent blood feeding. In this transmission cycle, mammals like horses and humans act as incidental dead-end hosts that cannot re-transmit the pathogen to its carrier.

It was previously reported that the virus is associated with high temperatures in spring and summer, warm winters, and droughts in summer. At the same time, the local circulation of the West Nile virus in Europe has been shown to depend on whether conditions are long-term; the effects of climate change have not been quantified.

Spatial Expansion of West Nile Virus

At the University of Brussels, a team of researchers explored the extent to which climate change has affected the spatial expansion of WNV across Europe. They account for other direct human influences like land use and changes in human population. The details of their study are described in the paper "Contribution of Climate Change to the spatial expansion of West Nile virus in Europe."

Led by Diana Erazo and Simon Dellicour from the Spatial Epidemiology Laboratory, the research team adopted a machine learning approach to predict the risk of local circulation of the West Nile virus. They also investigated the isolated effect of climate change by comparing factual simulations to a counterfactual one in which climate change had been eliminated.

According to Erazo, their findings indicate a significant role for climate change in the establishment of WNV in the southeastern part of Europe. In particular, the research team identified that current West Nile virus hotspots on the continent are most likely to be attributed to climate change.

The results also reveal a recent and drastic population increase at risk of exposure. Although an increase in population density partly brings about the increase, the team noted that climate change has also been a critical factor that drives the risk of WNV exposure in Europe.

Climate change has emerged as a critical public health challenge in our modern society. Dellicour believes that future studies should focus on the evolution of infectious disease distribution under various future climate change scenarios. The data that these studies will provide can be beneficial in designing surveillance and intervention strategies.