"If you see anything that's wiggling like this, it's mosquito larvae, dump it out," says Katherine Ramirez, the scientific education coordinator with Fresno County Mosquito Control.
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She adds: "It doesn't matter the area. We're finding the virus in all areas. It could be that your neighbor has an unmaintained swimming pool."
While these aren't fully grown mosquitoes, Ramirez says mosquitoes are temperature-dependent, so the hotter the temperature the faster the development.
"That's why its important to check water sources on a daily basis when we have hot temperatures or at least once a week," she says.
While some are just a nuisance, of the 30 types of mosquitoes found in Fresno County, four have the potential to carry and transmit West Nile Virus.
Symptoms include a fever, head or body ache, and joint pain.
But according to the CDC, 8 out of 10 people infected with West Nile won't develop symptoms.
That was the case with three of Fresno County's positive cases who found out after donating blood.
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Surveillance teams with Fresno County Mosquito Control set 200-250 traps weekly. Throughout this season they've collected 216 samples that have tested positive for West Nile.
One common household mistake that attracts mosquitoes is leaving shoes close to your doorway.
"Mosquitoes are attracted to the smell of our feet so mosquitoes are going to wait at the shoe and when you open the door they will follow you inside," says Ramirez.
Experts say it's important to remember dawn and dusk are when mosquitoes that carry West Nile are most active.
Make sure your insect repellent has DEET, lemon eucalyptus or picaridin.