DOWNEY — A mosquito sample collected in Downey has tested positive for West Nile virus, officials announced. 

The sample was taken in August and brings the total number of positive cases to 40 in Los Angeles County. 

About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.

Residents are urged to control the mosquito population around their homes by eliminating standing water and changing the water in their pet dishes often.