High incidence of human West Nile Virus infection and risk of mortality, 2003; high Plains/Panhandle, TX

Abstract

Purpose We seek to explain the high incidence of human West Nile Virus (WNV) infection, and risk of morbidity and mortality, reported from the Panhandle and South Plains regions of Texas in 2003, compared with the rest of the state. A 10-fold increase in human WNV meningoencephalitis cases was reported from this area in 2003, compared with 2002. Information gained will be used to improve area health education, disease surveillance, and medical treatment efforts in a largely medically underserved region. Methods Descriptive techniques and measures characterized the 2003 human WNV cases by person and place within the 41 counties that comprise this region of Texas. These data were age-adjusted for comparison with the remainder of the state. Data from environmental and entomologic sources were also used to provide other quantitative and qualitative explanations for the higher adjusted risk. Results In 2003, this region of Texas reported 24.2% ( n = 105) of the state's 434 cases of WNV meningoencephalitis, from 3.6% of the state's population. The patients were 76.8% Caucasian, 21.2% Hispanic, and 2.0% African American and ‘other’; age range was 12 to 87 years (mean, 54.4; median, 57); 60% were male. Of the 105 cases, 16 (15.2%) died as a result of their WNV infection. Dates of onset were earlier in 2003 than in 2002. In addition, in this region, 170 cases of WNV fever were recorded in 2003 (age range: 6–89 years; mean, 43.2; median, 43.0). In addition, 19 flavivirus and 14 St. Louis encephalitis viral infections were recorded from this region. We have tabular and graphical data presenting incidence (crude, age-specific, and age-adjusted), morbidity, and mortality rates. Conclusion We believe there are three primary explanations for an increased risk of human WNV infection and disease in this region of Texas: a human population that is significantly older than the remainder of the state; large areas of irrigated agricultural land and playa lakes that support varied populations of mosquito species close to human habitation.