Minimize the number of people with locally acquired West Nile virus

This is measured by tracking incidents of locally acquired West Nile virus cases and reporting as cases per 100,000 people

How are we doing?

Through routine surveillance, treatment and investigations of mosquito breeding sources and illness, the Department of Environmental Health Vector Control Program reduces the risk to public health.
The progression of West Nile virus (WNV) in San Diego County began in 2003. The first confirmed locally acquired human case of WNV in San Diego County was in 2006. West Nile virus is now the most prevalent mosquito-borne disease in the United States and in California. 
San Diego County continues to be below Statewide detections of WNV with a 2018 incidence rate of locally acquired WNV at 0.06 per 100,000 people as compared to the California overall WNV incidence rate of 0.55 per 100,000 people.  In 2019 the incidence rate remained low in San Diego County with a incident rate of locally acquired WNV at 0.00 per 100,000 people as compared to the California overall WNV incidence rate of 0.54 per 100,000 people.

How is this measured?

Human cases of WNV are reported to both the County of San Diego's Health and Human Service Agency (HHSA) and to the California Department of Public Health (CDPH).  HHSA refers WNV cases to the Vector Control Program for investigation of mosquito activity and breeding sources to reduce the risk of transmission.  Human cases of WNV, acquired locally  or outside of the county, are posted on
On a quarterly basis, the number of human cases are divided by the population of the county and multiplied by 100,000 to determine the incidence rate. The incidence rate is then compared to the stateside rate found at CDPH website. This year's WNV activity as well as information for prior years is available at (The case count presented is based on reporting dates to HHSA and CDPH and does not reflect disease onset dates)

Why is this important?

The Vector Control Program implements an integrated, risk-based response designed to promote safe and livable communities as well as to educate and involve business, organizations and property owners in the year-round effort to control mosquito breeding and minimize environmental, economic and health impacts associated with West Nile virus.

Where are we going?

Vector Control Program staff monitors for West Nile virus by routinely trapping for mosquitoes, testing batches of mosquitoes and dead birds. The program continues to monitor and treat over 1,500 known mosquito breeding sources in the county, to investigate year round neglected swimming pools and spas, and to collaborate with the public to Fight the Bite! 
In order to keep yourself, family and neighbors safe from mosquito-borne diseases, follow these three simple steps: Prevent, Protect and Report!
  1. Prevent mosquito breeding around your home.
  2. Protect against mosquito bites by using mosquito repellents and wearing long sleeves and pants.
  3. Report mosquito breeding sites like neglected swimming pools, spas and other standing water in your neighborhood.

The Department of Environmental Health (DEH) enhances San Diegans' quality of life by protecting public health and safeguarding environmental quality, educating the public to increase environmental awareness, and implementing and enforcing local, state, and federal environmental laws.  For more information visit our website at