The Incidence of West Nile Disease in Russia in Relation to Climatic and Environmental Factors

Abstract

Since 1999, human cases of West Nile fever/neuroinvasive disease (WND) have been reported annually in Russia. The highest incidence has been recorded in three provinces of southern European Russia (Volgograd, Astrakhan and Rostov Provinces), yet in 2010–2012 the distribution of human cases expanded northwards considerably. From year to year, the number of WND cases varied widely, with major WND outbreaks in 1999, 2007, 2010, and 2012. The present study was aimed at identifying the most important climatic and environmental factors potentially affecting WND incidence in the three above-mentioned provinces and at building simple prognostic models, using those factors, by the decision trees method. The effects of 96 variables, including mean monthly temperature, relative humidity, precipitation, Normalized Difference Vegetation Index, etc. were taken into account. The findings of this analysis show that an increase of human WND incidence, compared to the previous year, was mostly driven by higher temperatures in May and/or in June, as well as (to a lesser extent) by high August-September temperatures. Declining incidence was associated with cold winters (December and/or January, depending on the region and type of model). WND incidence also tended to decrease during year following major WND outbreaks. Combining this information, the future trend of WND may be, to some extent, predicted, in accordance with the climatic conditions observed before the summer peak of WND incidence.

Spatio-Temporal Identification of Areas Suitable for West Nile Disease in the Mediterranean Basin and Central Europe

“…In particular, in Russia, the model indicated the provinces of Astrakhan, Volgograd, and Rostov as at major risk. Actually, these provinces represent the “core” of WNV circulation in Russia, accounting for the 58% of the 2,283 human cases recorder in the country from 1999 to 2013 [ 72 ].…”

The Global Ecology and Epidemiology of West Nile Virus

“…In Hungary, the sudden spread of the virus in 2008 caused 12 equine and 22 human neuroinvasive cases [ 234 ]. Following the large outbreak in 1999, Russia experienced annual summer transmissions with sporadic outbreaks primarily in the south [ 242 ]. The three most affected regions were Astrakhan, Rostov, and Volgograd provinces with outbreaks in 2007, 2010, and 2012, although recently the range of the virus has apparently expanded, with cases reported further north- and eastward in several provinces including southern parts of Siberia [ 166 ].…”

The Role of Temperature in Transmission of Zoonotic Arboviruses

“…Within the main portion of the arboviruses’ range and along the cooler edge, an increase in temperature is typically associated with an increase in arboviral activity. For example, WNV infection rates north of 30° N, have been associated with increased temperatures [118,150,154,155,156,158,159,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193]. An increase with increasing temperatures has often been found for JEV as well [16,194,195,196,197,198,199], as has SLEV [200,201].…”