West Nile virus infections confirmed in Fresno County

Fresno County has confirmed dozens of mosquito samples have tested positive for West Nile virus, with a few humans infected.

Three people in Fresno County have been confirmed to be infected with West Nile virus this year. 

The Fresno County Department of Public Health announced that all three people have asymptomatic infections. 


The big picture: The three infections were found through routine blood donor testing. 

  • So far 56 mosquito samples have tested positive for West Nile virus this year, according to the Mosquito Abatement Districts in Fresno County. 
  • The Department of Public Health expects the number of cases in humans to increase as mosquito season hits full force. 

Zoom out: Last year there were 433 reported symptomatic human West Nile virus cases in California, according to the California Department of Public Health. 

  • That resulted in 19 deaths across the state and 40 asymptomatic infections in blood donors. 
  • Over 8,000 people have been infected with West Nile virus since it was first introduced into California in 2003, with over 390 deaths. 

What to do: The Fresno County Department of Public Health recommends the following precautions: 

  • Apply an EPA registered insect repellent that contains DEET, picaridin, oil of lemon eucalyptus or IR 3535, especially at dawn and dusk when mosquitoes are most active and follow the label instructions.
  • Make sure that doors and windows have tight-fitting screens to keep out mosquitoes and repair or replace screens that have holes.
  • Eliminate standing water and containers that can hold water from around the home.
  • Contact your MAD to report poorly maintained swimming pools or water features that appear green.

What they’re saying: “We need to stay vigilant as mosquitoes may continue to cause severe illnesses, including WNV infection, which can require hospitalization and intensive care,” says Dr. Rais Vohra, Fresno County Interim Health Officer. 

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