For the first time in 10 years, the Tarrant County health department is spraying for mosquitoes to prevent the spread of West Nile virus.
The ground spraying will target adult mosquitoes in unincorporated parts of the county. The spraying begins at 9 p.m.
Several cities in Tarrant County have also conducted ground spraying.
Tarrant County Public Health said the West Nile outbreak in North Texas this year has been unpredictable.
"There were no predictions of this," said David Jefferson, TCPH environmental health manager. "The last couple of years there has been virtually no activity. This just came out of left field and caught everyone by surprise."
As of Monday, the county had 250 reported human cases of West Nile virus and five deaths, in stark contrast to the single-digit human cases two years ago.
None of this year's deaths were from the unincorporated areas the county is ground spraying this week, but the spraying is intended to be preventative.
"The citizens have made their interest known to the commissioners, and they are responding," Jefferson said.
The county will spray in the northeast, west and south parts of the county starting Monday night and going until Friday.
Spraying will take place between 9 p.m. and 5 a.m.
The county will start with one truck and add more as the week goes on, with as many as three to four trucks out at the same time.
The county is using Anvil 2+2, which it said is one of the less intrusive chemicals for killing mosquitoes.
"By the next day when the sun comes up, any of the product that is remaining will be deactivated by the sun's light anyway," Jefferson said.
The county said it would not conduct aerial spraying because too many cities do not want it and it would be too difficult to avoid them.