DALLAS (August 14, 2012)--The first aerial spraying of insecticides in the Dallas area since the 1960s begins this week as health officials try to stem the worst outbreak of West Nile virus in the nation so far this year.

An official with the company hired to spray for mosquitoes in Dallas County said at least two planes will be in position by Thursday evening.

Clarke spokeswoman Laura McGowan said Tuesday that the chemical, synthetic pyrethroid, will be spread in small amounts and is safe for residents.

Truck spraying continued Monday in Dallas County, where 10 deaths have been attributed to West Nile virus this year.

Mosquitoes carry the virus from birds to humans.

The last time Dallas County restored to aerial spraying was in 1966 during an encephalitis outbreak that killed more than a dozen people.