Arlington is doing targeted ground spraying in areas where larvicide has not been effective.
Arlington officials plan to spray insecticide Tuesday night in three areas of the city for round three of its fight against mosquitoes infected with West Nile virus.
Crews are scheduled to spray around the University of Texas at Arlington, Martin High School and the Arlington Municipal Airport, weather permitting.
The city has 49 human cases of West Nile virus. As of Tuesday, North Texas has 662 human cases of the virus and 18 fatalities.
"Right now, we're seeing some localized groupings of some human West Nile cases," Fire Chief Don Crowson said. "Our teams have been going out there and communicating with the public and deploying larvicide, trapping and testing for mosquitoes."
City spokeswoman Rebecca Rodriguez said the city is doing targeted ground spraying in areas where larvicide has not been effective. The spraying effort includes backpack spraying, as well as teams on four-wheelers and in trucks.
The city said the insecticide used in the spraying does not pose a significant health risk but urged residents to stay indoors during the spraying hours of 10:30 p.m. and 4 a.m.
"We're concerned about collateral impacts of the spray, so we're trying to limit those impacts on fish, insects, pets and, certainly, citizens who have breathing issues," Crowson said.
Rain Tuesday night would cancel the planned spraying. Rodriguez said rain could be a mixed blessing.
"The rain is going to sweep out the drainage areas where you may have had some larvae -- that's the good news," she said. "What it's also going to do is create puddles and areas where the life cycle begins again for the mosquitoes, so, once again, we're going to urge residents to drain, make sure there's no standing water on your properties."
"I think the challenge is staying on top of the movement of the virus," Crowson said. "The fact is that if you can identify the trends early, you can aggressively deal with the issue."
The city said it could take a few days to a few weeks to know the effectiveness of the localized spraying efforts.