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07.27.16: San Gabriel Valley Mosquito and Vector Control District Detects West Nile virus in Mosquitoes

Mosquito samples collected from the cities of West Covina and Pomona have tested positive for West Nile virus (WNV). This confirms that mosquitoes in the San Gabriel Valley are actively circulating the virus and people are at risk of being infected. 

These are the first WNV-positive mosquito samples collected this year within the San Gabriel Valley Mosquito and Vector Control District’s boundaries. Mosquitoes were collected on July 20, 2016 in traps placed at Cortez Park in West Covina (located at Citrus St and Cortez St.) and at Cal Poly Pomona in traps placed at the northeast, east, and the southern parts of campus.  The District had identified WNV in a dead American crow collected on June 23, 2016 from Altadena and another on July 11, 2016 in Monrovia. The District is continuing with surveillance activities and increasing control efforts as it prepares for more WNV activity. The District’s Scientific Programs Manager Dr. Wakoli Wekesa says, “With the current heat wave in full swing we anticipate more WNV activity in the District and caution all residents to be vigilant as this will be a very busy season.”  

The best precaution against WNV is to prevent mosquito bites. All residents within the District and especially those living near or visiting Cortez Park and the University should take precautions by using mosquito repellents, wearing long sleeve shirts and long pants when outdoors between dusk and dawn, and ensure windows and doors are properly screened to keep mosquitoes out.

Since its introduction in 2003, WNV has infected more than 5,588 people and caused 229 deaths statewide, according to the California Department of Public Health. West Nile virus is endemic in California and presents a risk to public health every year.

It is critical that residents remove all standing water on their property to prevent mosquito production. Mosquitoes lay their eggs in stagnant water such as neglected pools, buckets, miscellaneous containers, puddles, and ponds. Eggs can hatch and develop into biting adults in four to seven days.

Throughout the summer, basic protective measures should be followed:

  • Wear mosquito repellent and protective clothing when outdoors while mosquitoes are active (especially around dawn and dusk).
  • Regularly inspect property to identify and remove sources of standing water where mosquitoes lay their eggs and grow.
  • Ensure doors and windows are properly screened.
  • Report increased mosquito activity, sources of standing water, and green pools to the District at (626) 814-9466 or online at


The District encourages the public to help identify WNV "hot spots" by reporting dead birds to the WNV Hotline at (877) WNV-BIRD ((877) 968-2473) or online at

For more information please visit the District’s website at and follow on social media @SGVmosquito.