With the number of human cases of West Nile virus still climbing, Tarrant County cities are escalating measures to kill mosquitoes,the source of the sometimes-deadly disease.For the first time since the 1990s, Fort Worth officials are making plans for ground-level spraying of insecticide targeting adult mosquitoes. Larval forms of the insect are killed through application of other chemicals in their hatching pools and through other measures.In Dallas, officials are moving ahead with what experts say can be a more effective -- but more expensive -- way of fighting the adult pests: aerial spraying. The Texas Department of State Health Services says it will help by providing airplanes, chemical spray and crews.State, county and local public health officials have decided these increased measures are necessary because of increased findings of West Nile virus in mosquitoes snared in traps.That considered assessment is aimed at public safety. As of Wednesday, there were 181 reported cases of West Nile virus -- and had been two deaths -- in Tarrant County alone. In Dallas County, the count has reached at least 190 cases and 10 deaths.The escalation in spraying is part of a hierarchy of countermeasures recognized by the federal Centers for Disease Control and Prevention.Still, there's no reason to panic. The CDC says only about 1 in 150 people infected by West Nile will develop serious illness. It's just that severe cases can lead to death or permanent neurological damage.Although this summer has seen a serious outbreak of West Nile, the most effective ways of reducing the threat are those taken by individuals to protect themselves and eliminate standing water where mosquitoes can hatch.Spraying, whether from the back of a truck driving down neighborhood streets or from a low-flying airplane, has only limited effectiveness."For adult mosquito control, insecticide must drift through the habitat in which mosquitoes are flying in order to provide optimal control benefits," a CDC report says. Spraying from the street might reach mosquitoes that happen to be airborne at the time in a home's front yard but not reach those in back.Bedford is one of the Tarrant County cities sending out trucks to spray. During a discussion of that decision at Tuesday's City Council meeting, Mayor Pro Tem and retired physician Roy Turner said spraying is "not much value by itself," although he agreed it's the proper step in the hierarchy of options open to the city now.The spray that lands on plants has little staying power and won't kill mosquitoes the next day.Many people worry about exposure to insecticide during spraying for mosquitoes. The Environmental Protection Agency says the chemicals used in the process, applied in the proper quantities and through proper techniques, don't pose unreasonable health risks to humans, wildlife or the environment.But even with that assurance, state health department officials advise staying indoors while spraying is going on and keeping doors and windows closed.The single most effective weapon in the anti-mosquito arsenal, according to the CDC and state and local health officials, is eliminating the standing water where larvae grow into adults. The experts call it "source reduction," which the CDC report says includes "activities as simple as the proper disposal of used tires and the cleaning of rain gutters, bird baths and unused swimming pools by individual property owners."That, plus spraying mosquito repellent on exposed skin, wearing long sleeves and long pants and avoiding outdoor activities during the dusk-to-dawn hours when mosquitoes are most active should keep people safe.