After recent rains, mosquitos are now swarming all areas of the Valley.
Supervisor Dennis Leroy says they are scrambling to fog and set out traps to test the mosquitos for West Nile Virus.
"We are always concerned about West Nile," he said. "But these are flood water mosquitos that don't carry West Nile. They are more of a nuisance."
For 6-year-old Ammon Petersen of Gilbert, the "nuisance" cost him a week of school. He had an allergic reaction to a series of bites on his leg causing his foot to swell up.
"It was itchy and then it hurt," he said.
His mother Delores said he often has reactions to bug bites.
"Normally he has to wear long pants and long sleeves when he is outside," she said.
Vector Control will be fogging in Scottsdale, Gilbert, and areas of Phoenix at midnight.