 The mosquito most common for transmitting West Nile is the Colex tar salus. This mosquito is most active from sundown and throughout the night into the early morning hours. To help reduce your risk of getting West Nile virus, the health department recommends the following protective measures. Use insect repellent that contains DEET. Limit outdoor activities between dusk and dawn when mosquitoes are most active. Wear long pants and long-sleeved shirts when possible. Eliminate standing water around homes, buckets, flower pots, old tires, wading pools, and bird baths.