Climate change projections of West Nile virus infections in Europe: implications for blood safety practices - PubMed (original) (raw)

Climate change projections of West Nile virus infections in Europe: implications for blood safety practices

Jan C Semenza et al. Environ Health. 2016.

Abstract

Background: West Nile virus (WNV) is transmitted by mosquitoes in both urban as well as in rural environments and can be pathogenic in birds, horses and humans. Extrinsic factors such as temperature and land use are determinants of WNV outbreaks in Europe, along with intrinsic factors of the vector and virus.

Methods: With a multivariate model for WNV transmission we computed the probability of WNV infection in 2014, with July 2014 temperature anomalies. We applied the July temperature anomalies under the balanced A1B climate change scenario (mix of all energy sources, fossil and non-fossil) for 2025 and 2050 to model and project the risk of WNV infection in the future. Since asymptomatic infections are common in humans (which can result in the contamination of the donated blood) we estimated the predictive prevalence of WNV infections in the blood donor population.

Results: External validation of the probability model with 2014 cases indicated good prediction, based on an Area Under Curve (AUC) of 0.871 (SD = 0.032), on the Receiver Operating Characteristic Curve (ROC). The climate change projections for 2025 reveal a higher probability of WNV infection particularly at the edges of the current transmission areas (for example in Eastern Croatia, Northeastern and Northwestern Turkey) and an even further expansion in 2050. The prevalence of infection in (blood donor) populations in the outbreak-affected districts is expected to expand in the future.

Conclusions: Predictive modelling of environmental and climatic drivers of WNV can be a valuable tool for public health practice. It can help delineate districts at risk for future transmission. These areas can be subjected to integrated disease and vector surveillance, outreach to the public and health care providers, implementation of personal protective measures, screening of blood donors, and vector abatement activities.

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Figures

Fig. 1

Fig. 1

Temperature anomalies for July 2014

Fig. 2

Fig. 2

Districts with probable and confirmed cases of West Nile Virus infections, as of 20/11/2014. Note: An affected area is defined as an area with one or more autochthonous human WNV cases (neuro-invasive and non neuro-invasive), meeting laboratory criteria as per EU case definition’ (Directive 2008/426/EC). Probable and confirmed: A probable case is any person meeting the clinical criteria AND with at least one of the following two: − an epidemiological link; − a laboratory test for a probable case. WNV cases by country: Austria (1); Greece (15); Hungary (11); Italy (24); Romania (23); Bosnia and Herzegovina (13); Israel (17); Palestine (1); Russian Federation (29); and Serbia (76)

Fig. 3

Fig. 3

Predicted probability of districts with West Nile Virus infections for 2014

Fig. 4

Fig. 4

Receiver operating characteristic (ROC) curve of the probability of West Nile Virus infections in 2014

Fig. 5

Fig. 5

Predicted probability of districts with West Nile Virus infections based on July temperatures for A1B scenario projections for 2025 (a) and 2050 (b). Note: Among IPCC scenarios, the A1 scenario groups are distinguished by their technological emphasis. A1B represent a balance across all energy sources (intensive fossil and non-fossil energy)

Fig. 6

Fig. 6

New districts affected by West Nile Virus infections in 2025 compared to 2014. Note: Panel a: Confirmed: A confirmed case is any person meeting laboratory criteria for case confirmation. Panel b: Total (confirmed and probable): A probable case is any person meeting the clinical criteria AND with at least one of the following two: − an epidemiological link; − a laboratory test for a probable case

Fig. 7

Fig. 7

Estimated prevalence of West Nile Virus infections in the blood donor population (per 100,000) by districts for 2014 (a) and for 2025 (b). Note: The prevalence of infection in the (donor) population was calculated based on the European Up-Front Risk Assessment Tool (EUFRAT) developed by ECDC [49]

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