The first locally acquired human cases of West Nile virus (WNV) this year have been confirmed in the cities of Rialto and San Bernardino, the Department of Public Health announced Tuesday.

“West Nile virus can cause a serious illness in humans. Therefore, I urge residents to take precautions to protect themselves against mosquito bites” said San Bernardino County Health Officer Michael A. Sequeira, M.D.

WNV is transmitted to humans through the bite of an infected mosquito. Signs and symptoms of WNV may include fever, body aches, rash, nausea, vomiting, and headache.

Most people infected with the virus have no symptoms. However, people 50 years of age and older and individuals with diabetes, hypertension, who are immunocompromised or have a recent history of chemotherapy have a higher chance of getting sick and are more likely to develop complications.

The most effective way to avoid WNV infection is to prevent mosquito bites.

If you experience a sudden high fever (above 102°F), severe headache, or a stiff neck, seek medical help right away.

The risk of infection due to WNV typically increases from summer through early fall. Residents are encouraged to protect themselves from mosquito bites during outdoor activities, especially at dawn and dusk.

Residents can protect themselves from mosquito bites by taking the following precautions:

  • DRESS – Wear shoes, socks, long pants, and long-sleeved shirts that are loose fitting and light colored.
  • DRAIN – Remove or drain all standing water around your property where mosquitoes lay eggs, including birdbaths, ponds, old tires, buckets, clogged gutters, and puddles from leaky sprinklers.
  • DOORS – Make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or holes to prevent mosquitoes from entering the home.
  • REPEL – Use insect repellent that has ingredients approved by the EPA such as DEET, IR 3535, and Oil of Lemon Eucalyptus.
  • REPORT – Report green or neglected pools by calling the San Bernardino County Mosquito and Vector Control Program at (800) 442-2283. Press 3 when prompted.

For more information on West Nile virus, to report a standing water source, or to request a courtesy mosquito inspection, visit the San Bernardino County Mosquito and Vector Control Program at or call (800) 442-2283.

Additional County Update News – August 11, 2023