937. Medical Risk Factors for Severe West Nile Virus Disease, United States, 2008-2010
Session: Poster Abstract Session: Biomarkers and Risk Factors for Viral Infections
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Since it was first detected in the Western Hemisphere in 1999, West Nile virus (WNV) has become the leading cause of arboviral encephalitis in the United States. With the exception of increased age and history of solid organ transplant, risk factors for severe disease among persons infected with WNV have not been clearly defined.

Methods: We conducted enhanced surveillance to identify risk factors for severe illness (i.e., hospitalization or death) and for development of neuroinvasive disease (e.g., encephalitis, meningitis, acute flaccid paralysis) among all cases of WNV disease reported from selected states from 2008-2010. Multivariate logistic regression was used to identify pre-existing medical conditions independently associated with each outcome. Population attributable fractions (PAF) were calculated for medical conditions associated with severe illness.

Results: Of the 1,084 WNV disease case-patients included in the analysis, 703 (65%) were hospitalized, 636 (59%) had neuroinvasive disease and 53 (8%) died. After adjusting for age, sex, and race, medical conditions independently associated with severe illness included chronic renal disease (OR 5.6, 95% CI 1.7-19.0), history of alcohol abuse (OR 3.5, 95% CI 1.5-8.3), diabetes (OR 2.3, 95% CI 1.5-3.6), history of cancer (OR 2.1, 95% CI 1.2-3.8), and hypertension (OR 1.5, 95% CI 1.1-2.1). The highest PAF was estimated for hypertension (15%), followed by diabetes (13%), cancer (5%), renal disease (5%), and alcohol abuse (4%). With the exception of renal disease and cancer, the same factors were independently associated with developing neuroinvasive disease. After age adjustment, immune suppression (OR 2.7, 95% CI 1.305.7) and cardiovascular disease (OR 1.9, 95% CI 1.0-3.5) were independently associated with death.

Conclusion: Hypertension, diabetes, chronic renal disease, and history of cancer or alcohol abuse were independently associated with increased risk of severe WNV disease. As many as one out of every fourth case of severe WNV illness may be attributable to hypertension or diabetes. Public health prevention messages should be targeted to persons with these conditions as well as previously established risk factors of older age and solid organ transplantation. 

Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

Nicole Lindsey, MS, J. Erin Staples, MD, PhD, Jennifer Lehman and Marc Fischer, MD, CDC, Fort Collins, CO


N. Lindsey, None

J. E. Staples, None

J. Lehman, None

M. Fischer, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.