Don't let them breed.Standing water gives mosquitoes a place to lay eggs. In your yard, turn over wading pools and wheelbarrows and clean the gutters. Have a birdbath? Change the water every other day.
Screen visitors.Tightly fitting screens (no holes) are a must for doors and windows. If you can, stay inside between dusk and evening (5 to 9 p.m.), when mosquitoes are hungriest. If you do go out at night and it's not too hot, dress your child in a long-sleeved shirt and pants.
Repel!Products that contain DEET (diethyltoluamide) last longest. But don't reapply them, and when everyone's inside, wash treated skin with soap and water. Or go natural: Botanical repellents with soybean oil work for about 90 minutes and are safe to reapply.
Even when you've done all of this, your little one will get bitten at times, of course. Just wash the area with soap and water, and ease the itch with calamine or cortisone cream. As for the West Nile virus, remember that it's still quite rare. But do call the doctor if your child gets a fever or feels achy after being bitten.