West Nile Virus and Mosquito Prevention

What is West Nile Virus?

West Nile Virus (WNV) is a mosquito-borne disease that was originally found in Africa, and as of 1999 has moved to the United States. Approximately 80% of people do not develop any symptoms, however about 1 in 5 will get flu-like symptoms that last for a few days, with fatigue and weakness that can last for weeks or months. In a very small percentage of people, <1%, severe neurological illness, such as encephalitis or meningitis (inflammation of the brain or surrounding tissue) may occur. They may last several weeks or become permanent, however, this happens in roughly 1 in every 150 people. Animals are also susceptible to WNV, including dogs and cats, but especially horses. To learn more about WNV and horses click here

The main way that people contract WNV is a bite from infected mosquitos. WNV cannot spread through touching.

Mosquito Prevention

There are three main ways to reduce the risk of being infected by WNV:

  • Use insect repellent: DEET, picaridin, or oil of lemon eucalyptus is recommended. 
  • Protect yourself most DAWN and DUSK: mosquitoes are more likely to bite during the early morning and evening, so make sure you wear proper clothing and repellent if outside during these times.
  • Drain standing water: mosquitoes lay eggs on standing water; so it is important to eliminate or drain all standing water sources around homes and properties.

Currently, there is no vaccine for WNV; the best method of not contracting the disease is to prevent contact with mosquitoes using the above methods. 


  1. Mosquito Fish
  2. Mosquito Biology
  3.  Home/Garden Prevention
  4. Larvicide Program
  5. Insect Repellents

Mosquito Fish can consume large quantities of insect larvae in your pond or other standing bodies of water. By reducing the mosquito population, you can reduce your risk of contracting mosquito-borne diseases including the West Nile Virus.

These fish are not native, they are invasive species. These fish are only meant for closed/stagnant ponds. They should not be placed into ponds that can drain into the local creeks and streams. This can have negative impacts on the native ecosystem. If your pond has outlets, please do not acquire these fish. FB Mosquito Fish

2022 Mosquito Fish Give Away Information

Printable Flyer: Mosquito Fish Give Away

Dates: Thursdays

  • May 5th
  • May 19th 
  • June 2nd 
  • June 16th 
  • June 30th

Time: 

All giveaways are from 12:00- 2:00 pm

Location: 

Eric Rood Administration Center, 950 Maidu Ave., Nevada City, CA. 

Drive Through Style & Fish Transport:

Please remain in your car. Containers will be provided to safely take fish home.

Request Mosquito Fish:

Please call (530) 265-1500

Please refer to our Frequently Asked Questions for more information, or contact us via phone at (530) 265-1222 or email at Env.Health@co.nevada.ca.us