After years of declining infection rates the West Nile virus hit the headlines once again. Officials from Los Angeles, Orange, Riverside, San Bernardino and San Diego counties gathered Tuesday in Garden Grove to announce the assault against West Nile and the mosquitoes that transmit it.

Humans and animals contract West Nile virus from bites of infected female mosquitoes, which contract it by feeding on birds that have the virus in their blood.

The Central District Health Department (CDHD) has been working along with the Elmore County Interim Mosquito Abatement District to provide surveillance of mosquito populations.

“In areas where West Nile virus has been detected, only a small proportion of mosquitoes are likely to be infected. Most people bitten by an infected mosquito do not become sick. Less than 1 percent of all people who are infected will become seriously ill,” according to Virginia Department of Health.

Officials believe the high rate of infections could be caused by swimming pools left neglected. That’s probably the reason why the virus is spreading in urban and suburban Southern California. Pools are the perfect breeding grounds for mosquitoes. The latest survey showed that more than 386 pools out of 950 are green or half-empty.

Central District Health Department officials recommend applying insect repellent containing DEET on exposed skin and clothing as well as avoiding exposure at dusk and dawn. Elderly people were asked to pay more attention, as they are more likely to develop severe complications, as their immune system is weakened.