CA Dept. of Public Health UC Davis Arbovirus Research and Training Mosquito and Vector Control Assoc. of CA

Case Counts by County

CountyDead birds
Contra Costa-
Del Norte-
El Dorado-
Los Angeles1
San Benito-
San Bernardino-
San Diego-
San Francisco-
San Joaquin1
San Luis Obispo-
San Mateo-
Santa Barbara-
Santa Clara5
Santa Cruz-

WNV Activity by County
Printable Version
2020 | 2019 | 2018
2017 | 2016 | 2015
2014 | 2013 | 2012
2011 | 2010 | 2009
2008 | 2007

Repellent Info

Last Updated: Mar 8, 2008

  • Why Should I Use Mosquito Repellent?
  • Insect repellent helps reduce your exposure to mosquito bites that may carry West Nile virus or other diseases, and allows you to continue to play, work, and enjoy the outdoors with a lower risk of disease.

back to top

  • When Should I Use Mosquito Repellent?
  • Apply repellents when you are going to be outdoors and will be at risk for being bitten by mosquitoes, especially around dawn and dusk when mosquitoes are most active. If you're outside during these hours pay special attention to using repellent. The safest decision is to use repellent whenever you are outdoors, even if it is only for a few minutes.

back to top

  • Which Mosquito Repellents Work Best?
  • A wide variety of insect repellents are available. The U.S. Centers for Disease Control and Prevention (CDC) recommends using only products containing active ingredients that are registered with the U.S. Environmental Protection Agency (EPA) for use as repellents. Registered products have been reviewed and approved for safety and effectiveness when used according label instructions. According to the CDC, the most effective repellents contain one of the following EPA registered active ingredients:
    • DEET (N,N-diethyl-m-toluamide)
    • Picaridin or KBR 3023 (2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester)
    • Oil of lemon eucalyptus or PMD (para-Menthane-3,8-diol)
    • IR3535 (3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester)
    For more information on these active ingredients, please visit the EPA Website.

back to top

  • How Do I Choose a Repellent?
  • Repellents are available in different concentrations. A product with a higher percentage of active ingredient (such as DEET) doesn't work better, it just lasts longer between applications. Choose a repellent that will provide protection for the amount of time you will be outdoors. You should use a higher- percentage product if you will be outdoors for several hours, or will be sweating, physically active, or getting wet. If your time outdoors will be limited, use a lower-percentage product; you can always re-apply if you are outdoors longer than expected. If you use a DEET-based product, one with a concentration of 30% is fine for most situations. To reduce the risk of adverse effects, you should use the lowest concentration product you can for your situation.

back to top

  • Are Repellents Safe?
  • DEET is the most widely available and tested repellent. Products containing DEET are very safe when used according to the directions. Because DEET is so widely used, a great deal of testing has been done. To read more information about DEET safety see the National Pesticide Information Center [NPIC], EPA re-registration eligibility decision fact sheet (

    General guidelines for using repellents safely:

    • Always follow the instructions on the product label.
    • Apply lightly but cover all exposed skin.
    • Don't apply repellent under clothing. You can apply repellent on clothing, but read the label first; some products stain fabric.
    • Do not spray aerosol or pump products in enclosed areas.
    • Do not apply aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.
    • Do not apply repellent to cuts, wounds, or irritated skin.
    • Wash treated skin with soap and water after returning indoors.

back to top

  • Can Repellents be used on Children?
  • You can use DEET products on children and on infants over two months old. The American Academy of Pediatrics (AAP) recommends using DEET products with a concentration of 30% or less on children. Picaridin and oil of lemon eucalyptus products can also be used on children but check the label-some should not be used on children under 3 years. When using repellents on children, apply to your own hands first and then put it on the child. Don't apply repellent to children's hands as they may put them in their mouth.

back to top

  • Can Repellents be used on Pregnant or Nursing Women?
  • The EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women.

back to top

  • What if I Have a Reaction to a Repellent?
  • Use of these products may cause skin reactions in rare cases. Cases of serious reactions to products containing DEET have been related to misuse of the product, such as swallowing, using over broken skin, and using for multiple days without washing skin in between use, for example. Whenever possible, wash skin between applications of repellent.

    If you suspect you or your child is having a reaction to a repellent, wash the skin and remove treated clothing. Then call your doctor or the local poison control center at: 1-800-222-1222.

back to top

  • Where Can I Get More Information About Repellents?
  • For more information about using repellents safely please consult the EPA Web site ( ) or consult the National Pesticide Information Center (NPIC), which is cooperatively sponsored by Oregon State University and the U.S. EPA. NPIC can be reached at or 1-800-858-7378.

back to top

Having problems with mosquitoes?

Locate your local mosquito and vector control agency
Search by Zip Code

Compared to previous year and previous five-year average to date

As of Jul 05, 2020202020195Y AVG
Human cases102
Dead birds2318142
Mosquito samples135471404
Sentinel chickens003
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2020 YTD activity -

WNV Reports

Weekly Report

07.06 Arbobulletin #12
07.05 2020 YTD SLEV Activity Map
07.05 2020 YTD WNV Activity Map


06.26 2003-2020 WNV Case Summary
03.02 2019 Human WNV Incidence Report
05.15 2018 Human WNV Incidence Report

Dead Birds

07.05Reported, Tested, Positive 2020
07.05Positive Species for 2020
07.05Positive Counts by City/County for 2020


10.04 AMOR - EVS Week 39
10.04 AMOR - GRAVID Week 39
10.04 AMOR - NJLT Week 39
- view report archives -