The Demographic and Socioeconomic Factors Predictive for Populations at High-Risk for La Crosse Virus Infection in West Virginia

Although a large body of literature exists for the environmental risk factors for La Crosse virus (LACV) transmission, the demographic and socioeconomic risk factors for developing LACV infection have not been investigated. Therefore, this study investigated the demographic and socioeconomic risk factors for LACV infection in West Virginia from 2003 to 2007, using two forward stepwise discriminant analyses. The discriminant analyses were used to evaluate a number of demographic and socioeconomic factors for their ability to predict: 1) those census tracts with at least one reported case of LACV infection versus those census tracts with no reported cases of LACV infection and 2) to evaluate significantly high-risk clusters for LACV infection versus significantly low-risk clusters for LACV infection. In the first model, a high school education diploma or a general education diploma or less and a lower housing densit

The spatial epidemiology and clinical features of reported cases of La Crosse Virus infection in West Virginia from 2003 to 2007

Background La Crosse virus (LACV) is a major cause of pediatric encephalitis in the United States. Since the mid-1980s, the number of reported cases of LACV infection in West Virginia has continued to rise and the state currently reports the most cases in the United States. The purpose of this study was to investigate and describe the spatial epidemiology and clinical presentation of LACV infection cases reported in West Virginia, as well as to provide a description of the environmental conditions present at the residences of the LACV infection cases. Methods Descriptive and spatial analyses were performed on LACV infection cases reported to the West Virginia Department of Health from 2003 to 2007. Clinical and environmental variables were available for 96 cases and residence data were available for 68 of these cases. Spatial analyses using the global Moran\u27s I and Kulldorff\u27s spatial scan statistic were performed using the population 15 years and younger at both the county and census tract levels to identify those geographic areas at the highest risk of infection. Results Two statistically significant (p \u3c 0.05) high-risk clusters, involving six counties, were detected at the county level. At the census tract level, one statistically significant high-risk cluster involving 41 census tracts spanning over six counties was identified. The county level cumulative incidence for those counties in the primary high-risk cluster ranged from 100.0 to 189.0 cases per 100,000 persons (median 189.0) and the census tract level cumulative incidence for those counties in the high-risk cluster ranged from 61.7 to 505.9 cases per 100,000 persons (median 99.0). The counties and census tracts within high-risk clusters had a relative risk four to nine times higher when compared to those areas not contained within high-risk clusters. The majority of LACV infection cases were reported during the summer months in children 15 years and younger. Fever, vomiting, photophobia, and nausea were the most commonly reported signs and symptoms. A case fatality rate (CFR) of 3.1% was observed. Wooded areas and containers were present at the majority of case residences. Conclusions The cumulative incidences of LACV infection from 2003 to 2007 were considerably higher than previously reported for West Virginia, and statistically significant high-risk clusters for LACV infection were detected at both the county and census tract levels. The finding of a high CFR and the identification of those areas at highest risk for infection will be useful for guiding future research and intervention efforts

Independent variables retained following the discriminant analysis comparing low-risk clusters for LACV infection to high-risk clusters for LACV infection and selected model parameters.

1<p>HSD: High school diploma.</p>2<p>GED: General education diploma.</p

Distribution of the cumulative incidence, cases, and clusters of reported La Crosse virus infections in West Virginia census tracts from 2003 to 2007.

<p>(A) Cumulative incidence of La Crosse virus infections, (B) Distribution of cases of La Crosse virus infection, and (C) Significantly high- and low-risk clusters for La Crosse virus infection.</p

Variables considered in the census tract and cluster discriminant analyses.

<p>*Mean of the variables considered in the census tract analysis comparing those census tracts with one or more reported cases of La Crosse virus infection to those census tracts without any reported cases of La Crosse virus infection.</p>†<p>Mean of the variables considered in the cluster discriminant analysis comparing those census tracts of significantly high-risk to those of significantly low-risk for La Crosse virus infection.</p>1<p>HSD: High school diploma.</p>2<p>GED: General education diploma.</p>3<p>>HSD/GED: Includes some college, associate degree, bachelor degree, graduate degree or professional degree.</p

Independent variables retained following the discriminant analysis comparing census tracts with no reported cases of LACV infection to those census tracts with at least one reported case of LACV infection and selected model parameters.

1<p>HSD: High school diploma.</p>2<p>GED: General education diploma.</p