Health Officials Issue Mosquito Warning

County health officials are urging residents to defend against mosquito-borne illness by emptying containers of standing water and ensuring that all swimming pools are properly filtered and maintained.

With the advent of warmer, wet weather, the Los Angeles County Department of Health Services said Wednesday that mosquitoes are becoming more active and pose a potential health risk. Mosquitoes can carry and transmit encephalitis, a potentially deadly virus that causes inflammation of the brain and spinal cord.

Gail Van Gordon, a department entomologist, said even the smallest sources of water can breed mosquitoes if they are left standing for up to a week. Sources of standing water include buckets, old tires, wheelbarrows and planters. Pools that are improperly filtered or lack the necessary chemical additives will breed insects as well.

County health officials say the last case of a human infected with encephalitis occurred in 1997. The last time such an infection resulted in death was 1984.

Mosquitoes exist year-round, but activity and breeding are highest from May to October. During this period it takes roughly one week for a mosquito to grow from an egg to an adult.

Mosquitoes were unusually prevalent last year because of El Nino rains.