Even as Dallas County moves to more aggressively combat an epidemic of West Nile virus from the air, Tarrant County's huge increase in cases in a matter of weeks hasn't changed officials' decision to stand pat.Largely, that means telling the public to wear pants and long sleeves and stay indoors at dusk and dawn while several cities continue targeted spraying of mosquitoes.Dr. Sandra Parker, Tarrant County Public Health medical director and health authority, said additional response strategies, depending on the situation, may result in "other types of concentrated spraying or even declaring an emergency, which can give you an opportunity for additional resources for combating the virus."However, in mid-July, when 16 cases had been reported in Tarrant, Parker told the Star-Telegram, "This fits the definition of an epidemic." By late July, there were 30 reported cases.By Friday, reported cases had jumped to 146.On Thursday, Dallas County Judge Clay Jenkins declared a public health emergency in his capacity as the director of homeland security and emergency management. The county plans to file a disaster declaration with the state and request resources to help control the virus."This declaration will expand our avenues for assistance in our ongoing battle with West Nile Virus," Jenkins said in a statement."While we are busy doing everything we can to keep residents well informed and as protected as possible, we need your help."Jenkins announced Friday that state planes have been requested and would spray the densely populated northern part of Dallas. Earlier in the week, Dallas County commissioners rejected a physicians group's request for immediate spraying.It would be the first time since the mid-1960s that Dallas has used aerial spraying.The planes would spray insecticide on the highly infested northern part of Dallas as well as Highland Park and University Park -- where mosquito pools are concentrated.But they wouldn't be used until leaders in those jurisdictions approve, said Jenkins, who urged officials to allow them. Jenkins said a request for 40 additional trucks and 80 professionals remains in effect.Dr. David Lakey, commissioner of the Texas Department of State Health Services, supported Jenkins' actions, saying, "Currently there is an historic outbreak of the West Nile virus in Dallas County. ... We want to ensure that all tools for an effective response to the outbreak are available."Dallas and Tarrant counties have been hard hit by West Nile this year. As of Thursday, Dallas County reported 175 human cases and nine deaths, seven of those reported from July 27 through Wednesday, according to Dallas County Health and Human Services.The West Nile outbreak in Tarrant this year now totals more than all cases in the county -- 128 combined -- from 2006 to 2011. This year, one Tarrant resident has died. In 2006, by contrast, Tarrant reported 53 cases that led to seven deaths.Tarrant County Judge Glen Whitley said he's in close communication with the health department, which in turn is monitoring the situation in cities.Whitley said he does not feel, based on the information he has, that a emergency declaration is warranted."We're just, again, trying to coordinate with different cities and have not felt we need to be looking at aerial spraying at this point in time," he said.Aerial-spraying issuesTarrant County officials said spraying is or has been conducted in Benbrook, Euless, Hurst, Westover Hills, North Richland Hills and Grand Prairie.Parker said aerial spraying, like ground spraying, has positive and negative consequences, such as killing off helpful insects.Parker said larvicides have been used in standing water to kill mosquito larvae.Mosquito eggs hatch when exposed to water, and the larvae live in water, usually surfacing to breathe, according to the Environmental Protection Agency.From 2002 to 2011, 1,331 cases of West Nile were reported, with 122 deaths, a mortality rate of just over 9 percent, according to the Texas Department of State Health Services. However, the figures do not appear to match those collected by county health departments.This year, large population centers Fort Worth and Arlington are far and away the leader in cases, with their 75 victims representing more than 50 percent of all incidents, according to Tarrant County Public Health statistics.About 1 in 5 people who become infected will develop West Nile fever. A few, especially the elderly, develop more serious complications.No vaccine is available for the virus, and treatment for severe cases includes hospitalization, intravenous fluids and airway management.Health officials also recommend staying indoors at dusk and dawn, dressing in long sleeves and pants, using insect repellent and draining standing water near your home.
Darren Barbee, 817-390-7126Twitter: @DarrenBarbee