Five people have died and 100 have been infected with West Nile virus in Los Angeles County this year, the highest caseload at this point in mosquito season since 2017.

The LA County West Vector Control District, which serves Manhattan Beach, Hermosa Beach, Redondo Beach, El Segundo and Hawthorne, is among the agencies responding as cases spread throughout the county. The district's Executive Director Aaron Arugay presented mosquito mitigation plans to the El Segundo City Council in January.

The Los Angeles County Department of Public Health announced the numbers Monday, Sept. 21, warning that the county is on track for one of its most severe West Nile seasons in recent years. In 2017, 268 infections were reported over the entire season, Patch reported, citing the county health department.

Nearly all of the 100 reported patients suffered severe illness affecting the brain or spinal cord, and almost all required hospitalization, according to the department. Officials said that is partly because milder cases often go undiagnosed and unreported.

Dr. Muntu Davis, the county health officer, called the number of severe cases and deaths "concerning" in a department statement. Davis urged residents to use insect repellent, eliminate standing water and check that window and door screens have no holes or tears.

There is no vaccine for West Nile virus. No specific treatment exists. The virus spreads through bites from infected mosquitoes, which pick it up from infected birds. Peak mosquito season in LA County runs from June through November.

About one in five infected people develops fever, headaches, body aches or rash. About one in 150 develops severe illness, including high fever, stiff neck, confusion or paralysis. People over 50 and those with underlying health conditions face the greatest risk. Symptoms typically appear three to 14 days after a bite.

Vector control agencies across the county have stepped up surveillance and mosquito-control treatments, San Gabriel Valley Mosquito and Vector Control District Manager Jason Farned said in the department's announcement.

Health officials recommend emptying standing water from flowerpots, birdbaths and outdoor containers at least once a week. Pools and spas should be properly maintained, and rain barrels should be covered. Federally registered repellents containing DEET, picaridin, IR3535, 2-undecanone or oil of lemon eucalyptus can help prevent bites.

Residents can call 2-1-1 to find their local vector control agency or report persistent mosquito problems. The county's Public Health InfoLine, 1-833-540-0473, is open daily from 8 a.m. to 8 p.m.