wnv infection is a reportable condition in texas , with clinical cases passively reported by physicians to the local health departments , which in turn report to texas department of state health services ( txdshs ) . we examined surveillance data for all reported cases for which symptom onset occurred during the 2012 calendar year , and we used descriptive statistics to describe the clinical features and demographic characteristics of reported case - patients . we calculated attack rates by sex , age , and race / ethnicity and incidence rates by county using population estimates for 2012 ( 3 ) . odds ratios ( ors ) , 95% cis , and p values were calculated to determine differences in demographic variables between severe disease ( wnv neuroinvasive disease [ wnnd ] , which included encephalitis , meningoencephalitis , and meningitis ) and less severe disease ( uncomplicated wnv fever ) . epi info 7.0 software ( centers for disease control and prevention , atlanta , ga , usa ) was used for all statistical calculations . a total of 1,868 cases were reported to txdshs during the 2012 transmission season ( table ) , including 844 ( 45% ) wnnd cases and 89 deaths ( case - fatality rate  5% ) . dates of onset ranged from may 1 , 2012 , through december 6 , 2012 ( figure 1 ) . the outbreak peaked during week 33 ( mid - august ) with 225 reported cases , which is historically the same peak for all reported wnv cases in texas during 20022011 ( 2 ) . the median time from date of symptom onset to date of official report to txdshs was 27 days ( range 6274 days ) . * attack rates based on 2012 population estimates from the texas state data center ( 3 ) when examining the demographic characteristics of the reported cases , we found significant differences in sex , age , and race / ethnicity with regard to severity of disease . overall , a higher percentage of male case - patients were reported ( 55% ) , and male case - patients were significantly more likely than female case - patients to have wnnd ( or  1.5 , 95% ci  1.21.8 , p<0.001 ) . median age of all case - patients was 54 years ( range 1 month100 years ) . persons > 65 years of age were significantly more likely than younger persons to have wnnd ( or  2.1 , 95% ci  1.82.6 , p<0.001 ) . the median age of the 89 case - patients who died was 79 years ( range 25100 years ) . when examining race / ethnicity of all cases , we observed the highest attack rate ( 11.1 cases/100,000 population ) in white , non - hispanics . however , minority populations were significantly more likely to have wnnd ( or  1.9 , 95% ci  1.62.4 , p<0.001 ) . of the 254 counties in texas , 135 ( 53% ) reported a wnv case ( figure 2 ) . almost half of the cases were reported from the northeastern quadrant of the state , including the dallas / fort worth metroplex ( 902 [ 48% ] cases ) : dallas ( 396 [ 21% ] ) , tarrant ( 259 [ 14% ] ) , collin ( 64 [ 3% ] ) , and denton ( 183 [ 10% ] ) counties . incidence rates per 100,000 population during west nile virus outbreak , texas , usa , 2012 . the 2012 wnv outbreak in texas was unexpected in terms of the magnitude of virus transmission and number of human cases . we recently observed a 3-year pattern of increases in reported human cases in texas , as seen in 2003 , 2006 , and 2009 ( 2 ) . in 2012 , the dramatic epidemic was consistent with this prior observation , with the 1,868 reported cases being more than double the historic high , which occurred in 2003 ( 735 cases ) . in addition to the dramatic increase in human cases in 2012 , the state also reported an increase in equine cases ( 121 cases in 2012 compared with 6 cases in 2011 ) . the exact factors that contributed to this epidemic are unknown and most likely complex , considering that successful transmission depends on supportive environmental conditions , vector abundance , avian reservoir and susceptible host abundance , pathogenicity of the virus , and sizeable populations of immunologically naive reservoir species . wnv more severely affects persons > 65 years of age ; deaths typically are reported in elderly presons ( 4,5 ) . during 2012 , there was some media speculation that more cases of severe disease occurred in younger persons and that the circulating strain of virus possibly was more pathogenic than in prior years . compared with texas data for 20022011 , we did not find any statistically significant differences in median ages of reported wnnd or fatal cases in 2012 using the kruskal - wallis 1-way analysis of variance on ranks . our findings from 2012 remain consistent with our experience from prior years ; however , it remains critical to emphasize the importance of recognizing disease and testing persons of any age who have clinical signs and symptoms consistent with wnv infection . the 2012 wnv outbreak in texas greatly affected the state economically . on the basis of the acute medical care and productivity loss cost estimates provided by barber et al . ( 6 ) ( adjusted to 2012 usd ) , we crudely estimate the 2012 outbreak in texas cost $47.6 million ( range $ 14.5$140.7 million ; technical appendix table ) . in addition to these acute costs , the outbreak also required an increase in resources for mosquito control and public health efforts to respond to the epidemic . a recent study reported the cost of aerial spraying alone in dallas county exceeded $ 1.6 million ( 7 ) . the long - term economic impact of this outbreak also is expected to be substantial as a consequence of long - term rehabilitation and disability costs ( 8) , possible risk for chronic kidney disease ( 9 ) , and risk for premature death in severe cases ( 10 ) . the unprecedented 2012 outbreak confirms the need for continued vigilance for surveillance to enable timely implementation of control measures to prevent virus transmission . we expect texas will continue to experience endemic levels of virus transmission with periodic epizootics . considering the economic and physical costs to persons severely affected , development of an effective vaccine is urgently needed to prevent disease . until a vaccine becomes available , public health authorities will need to maintain their focus on surveillance , disease recognition , implementation of control measures , and public education about protective measures .
during the 2012 west nile virus outbreak in texas , usa , 1,868 cases were reported . 
 male patients , persons > 65 years of age , and minorities were at highest risk for neuroinvasive disease . 
 fifty - three percent of counties reported a case ; 48% of case - patients resided in 4 counties around dallas / fort worth . 
 the economic cost was > $ 47.6 million .