Five counties within the Dallas-Fort Worth area - the fourth largest metropolitan area in the country - recorded 28 of the 63 deaths and 869 of the 1,429 cases reported to the Texas Department of State Health Services by Tuesday. Dallas County alone has recorded 16 deaths and 371 cases, according to county authorities.
CDC and state officials believe a year's worth of record high temperatures and intermittent rainfall this past spring contributed to the severity of the epidemic by affecting bird and mosquito populations. Following a record hot summer and drought conditions in 2011, Dallas-Fort Worth had a warm winter with fewer than normal freezes followed by bouts of rain in the spring, officials said.