Spatio-Temporal Epidemiology of Human West Nile Virus Disease in South Dakota

Michael Wimberly,Lon Kightlinger,Paolla Giacomo,Michael Hildreth

doi:10.3390/ijerph10115584

Abstract

Despite a cold temperate climate and low human population density, the Northern Great Plains has become a persistent hot spot for human West Nile virus (WNV) disease in North America. Understanding the spatial and temporal patterns of WNV can provide insights into the epidemiological and ecological factors that influence disease emergence and persistence. We analyzed the 1,962 cases of human WNV disease that occurred in South Dakota from 2002–2012 to identify the geographic distribution, seasonal cycles, and interannual variability of disease risk. The geographic and seasonal patterns of WNV have changed since the invasion and initial epidemic in 2002–2003, with cases shifting toward the eastern portion of South Dakota and occurring earlier in the transmission season in more recent years. WNV cases were temporally autocorrelated at lags of up to six weeks and early season cumulative case numbers were correlated with seasonal totals, indicating the possibility of using these data for short-term early detection of outbreaks. Epidemiological data are likely to be most effective for early warning of WNV virus outbreaks if they are integrated with entomological surveillance and environmental monitoring to leverage the strengths and minimize the weaknesses of each information source.

Highlights

Emerging infectious diseases, including those that have appeared for the first time, rapidly increased in incidence, or expanded into new geographic areas, are a significant concern in the fields of human and veterinary medicine as well as wildlife conservation [1,2]
We addressed the following specific questions: (1) Where in South Dakota is West Nile virus (WNV) risk highest and has this geographic pattern changed over time? (2) During what part of the year is WNV risk highest and has this seasonal pattern changed over time? (3) What are the temporal patterns of WNV anomalies and can they be used to predict future WNV risk?
To have sufficient data for the analysis, we focused on major outbreak years during which more than 200 WNV cases occurred in South Dakota (2003, 2005, 2007, and 2012)

Summary

Introduction

Emerging infectious diseases, including those that have appeared for the first time, rapidly increased in incidence, or expanded into new geographic areas, are a significant concern in the fields of human and veterinary medicine as well as wildlife conservation [1,2]. Disease emergence is often connected with the development of human societies and their interactions with the environment, including the proliferation of transportation networks that facilitate pathogen spread, land use and climate change that affect habitats for arthropod vectors, and animal hosts, and population movements that increase human and domesticated animal contact with wildlife and their pathogens. The successful invasion of North America by West Nile virus (WNV) is a well-known example of infectious disease emergence that was initially caused by long-distance pathogen transport and facilitated by a diversity of suitable environments for transmission [3]. In 2002 widespread WNV cases occurred in the Midwest and south-central states, and the first WNV cases were reported in

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