The emergence of West Nile Virus, as well as other emerging diseases, is linked to complex ecosystem processes such as climate change and constitutes an important threat to population health. Traditional public health intervention activities related to vector surveillance and control tend to be reactive and limited in their ability to deal with multiple epidemics and in their consideration of population health determinants. This paper reviews the current status of West Nile Virus in Canada and describes how complex systems and geographical perspectives help to acknowledge the influence of ecosystem processes on population health. It also provides examples of how these perspectives can be integrated into population-based intervention strategies.
Hydro-Quebec/NSERC Chair in Statistical Hydrology, Canada Research Chair on the Estimation of Hydrological Variables, University of Quebec, INRS-ETE, 490, de la Couronne, Quebec (QC) G1K 9A9, CANADA. email@example.com
In 2002, major human epidemics of West Nile Virus (WNV) were reported in five cities in the North East region of North America. The present analysis examines the climatic conditions that were conducive to the WNV epidemic, in order to provide information to public health managers who eventually must decide on the implementation of a preventive larvicide spraying program in Quebec, Canada. Two sets of variables, the first observed in the summer of 2002 and the second in the preceding winter were analysed to study their potential as explanatory variables for the emergence of the virus at epidemic levels.
Results show that the climatic conditions observed in the year 2002 have contributed to the emergence of the virus and can be observed once every forty years on average. The analysis has shown that the 2002 events observed in several North East North American cities are characterized by two main variables: the number of degree-days below -5 degrees C in the winter (DD-5) and the number of degree-days greater than 25 degrees C in the summer (DD25).
In the context of a declining rate of human and aviary infection to WNV, this element contributed to the decision to suspend the use of preventive larvicides in the province of Quebec in 2006 and for the foreseeable future. The second part of this study indicates that it is very important to estimate the risk that extreme values can be observed simultaneously in the summer and in the winter preceding the appearance of the virus. The proposed models provide important information to public health officials, weeks before the appearance of the virus, and can therefore be useful to help prevent human epidemics.
Western Nile fever (WNF) is an arboviral infection of the most relevance to the Volgograd Region. The observed decreasing incidence of WNF in 2001-2006, 2008, and 2009 and a decline in the number of its severe forms are only suggestive of the temporary regression of the epidemic process in the Volgograd Region. There are prerequisites and forerunners for a complication of the epidemiological Western Nile fever situation in the Volgograd Region. The goal of the epidemiological survey of Western Nile fever is to provide necessary and sufficient information for the analysis of the epidemiological situation and to define a line of public health policy and actions when making managerial decisions.
In 2003, an outbreak of West Nile virus (WNV) occurred in Saskatchewan, Canada from July to September. One-hundred thirty-three horse cases and 947 human cases were recorded and data were analyzed retrospectively for evidence of clustering to determine if clinical infection in the horse population could be used to estimate human risk of infection with WNV. Kulldorff's scan statistic was used to identify spatial-temporal clusters in both the human and horse cases. In most areas, human clusters were not preceded by horse clusters. In one area, a significant cluster of horse cases preceded human cases by 1 week; however, 1 week does not provide sufficient time for human-health authorities to act and provide advance warning for the public.
West Nile Virus (WNV) is a flavivirus, which was first isolated in Uganda 1937. This virus has attracted attention in the past years. WNV is one of the worlds most widespread flaviviruses and has caused recent outbreaks among humans and animals. West Nile Fever (WNF) is a mosquito borne zoonotic disease. The last decade the epidemiological pattern of the virus and the severity of the outbreaks have changed. This article reviews the epidemiological changes and current situation of WNF, presents a case report and evaluates the risk for a possible outbreak in Sweden.