Key Factors Influencing the Incidence of West Nile Virus in Burleigh County, North Dakota.

Hiroko Mori,Motomu Ibaraki,Joshua Wu,Franklin Schwartz

doi:10.3390/ijerph15091928

Abstract

The city of Bismarck, North Dakota has one of the highest numbers of West Nile Virus (WNV) cases per population in the U.S. Although the city conducts extensive mosquito surveillance, the mosquito abundance alone may not fully explain the occurrence of WNV. Here, we developed models to predict mosquito abundance and the number of WNV cases, independently, by statistically analyzing the most important climate and virus transmission factors. An analysis with the mosquito model indicated that the mosquito numbers increase during a warm and humid summer or after a severely cold winter. In addition, river flooding decreased the mosquito numbers. The number of WNV cases was best predicted by including the virus transmission rate, the mosquito numbers, and the mosquito feeding pattern. This virus transmission rate is a function of temperature and increases significantly above 20 °C. The correlation coefficients (r) were 0.910 with the mosquito-population model and 0.620 with the disease case model. Our findings confirmed the conclusions of other work on the importance of climatic variables in controlling the mosquito numbers and contributed new insights into disease dynamics, especially in relation to extreme flooding. It also suggested a new prevention strategy of initiating insecticides not only based on mosquito numbers but also 10-day forecasts of unusually hot weather.

Highlights

The West Nile Virus (WNV) is an arbovirus, which operates in a natural enzootic cycle between mosquito vectors and avian hosts [1]
This study identified key factors that contributed to variability in the mosquito numbers and WNV cases in Bismarck, North Dakota
Two independent Generalized linear models (GLMs) models are capable of predicting mosquito abundances and human disease cases, respectively

Summary

Introduction

The West Nile Virus (WNV) is an arbovirus, which operates in a natural enzootic cycle between mosquito vectors and avian hosts [1]. The absence of medical remedies for WNV points to the need for strong mosquito control programs for protection against the virus. Another important reason for focusing on WNV infections in humans is a large number of unprecedented outbreaks in the North-Western hemisphere. After the initial introduction of the virus in 1999, it spread across North America in just a few years. The virus has been responsible for more than 40,000 cases among humans within the U.S [3]. Its broad geographic distribution and ability to adapt to new habitats have raised concerns about the evident difficulties in controlling disease outbreaks

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Discussion

Conclusion