The 2012 West Nile Encephalitis Epidemic in Dallas, Texas

• Published in: JAMA : the journal of the American Medical Association 2013-07, Vol.310 (3), p.297-307
• Main Authors: Chung, Wendy M, Buseman, Christen M, Joyner, Sibeso N, Hughes, Sonya M, Fomby, Thomas B, Luby, James P, Haley, Robert W
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age Factors; Aged; Animals; Arboviral encephalitis; Arboviroses; Asthma - epidemiology; Biological and medical sciences; Child; Child, Preschool; Culex - virology; Disease Outbreaks; Emergency Service, Hospital - utilization; Encephalitis; Epidemics; Epidemiology; Exanthema - epidemiology; Female; General aspects; Geography, Medical; Housing; Human viral diseases; Humans; Incidence; Infant; Infectious diseases; Insect Vectors; Insecticides; Male; Medical research; Medical sciences; Middle Aged; Mosquito Control; Mosquitoes; Population Surveillance; Prevalence; Public health. Hygiene; Public health. Hygiene-occupational medicine; Retrospective Studies; Seasons; Texas - epidemiology; Tropical viral diseases; Viral diseases; Viruses; West Nile Fever - epidemiology; West Nile virus; West Nile virus - isolation & purification
• ISSN: 0098-7484; 1538-3598
• DOI: 10.1001/jama.2013.8267

IMPORTANCE After progressive declines over recent years, in 2012 West Nile virus epidemics resurged nationwide, with the greatest number of cases centered in Dallas County, Texas. OBJECTIVE To analyze the epidemiologic, meteorologic, and geospatial features of the 2012 Dallas West Nile virus epidemic to guide future prevention efforts. DESIGN, SETTING, AND PATIENTS Public health surveillance of Dallas County, an area of 2257 km2 and population of 2.4 million. Surveillance data included numbers of residents diagnosed with West Nile virus infection between May 30, 2012, and December 3, 2012; mosquito trap results; weather data; and syndromic surveillance from area emergency departments. MAIN OUTCOMES AND MEASURES Incidence and age-adjusted incidence rates of West Nile neuroinvasive disease (WNND), daily prevalence of emergency department visits for asthma and skin rash, and Culex quinquefasciatus species-specific vector index (an estimate of the average number of West Nile virus–infected mosquitoes per trap-night). RESULTS The investigation identified 173 cases of WNND, 225 of West Nile fever, 17 West Nile virus–positive blood donors, and 19 deaths in 2012. The incidence rate for WNND was 7.30 per 100 000 residents in 2012, compared with 2.91 per 100 000 in 2006, the largest previous Dallas County outbreak. An unusually rapid and early escalation of large numbers of human cases closely followed increasing infection trends in mosquitoes. The Cx quinquefasciatus species-specific vector index predicted the onset of symptoms among WNND cases 1 to 2 weeks later (count regression β = 2.97 [95% CI, 2.34 to 3.60]; P