The Los Angeles County Department of Public Health (Public Health) confirmed the first deaths due to West Nile Virus (WNV) this year in LA County (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments). The two residents were elderly males from the San Fernando Valley area, both hospitalized in August and died from WNV-associated encephalitis.

Culex mosquito
Culex quinquefasciatus

This week, 11 new WNV infections, including 2 asymptomatic blood donor, were documented in Los Angeles County, for a total of 68 infections this year. The number of WNV cases identified in Los Angeles County this year exceeds that identified by this time in 2015.

“This serves as a warning that West Nile virus is a serious disease that may lead to hospitalization and can even result in death,” said Jeffrey Gunzenhauser, MD, MPH, Interim Health Officer for Los Angeles County. “Older adults and people with weak immune systems are at highest risk of severe illness. Protect yourself from mosquitoes by using insect repellent containing an effective ingredient such as DEET, and eliminating any standing water around your home where mosquitoes can breed. Do it for your kids. Do it for your grandkids. Do it for yourself.”

Persons over 50 years of age and those with immunocompromising medical conditions are at increased risk of serious WNV infection, neuroinvasive disease (including meningitis, encephalitis, and paralysis) and death. In total, 108 human infections, including four fatalities, have been documented in the state of California in 2016.

Public Health performs surveillance to identify people with WNV, and collaborates with local vector control agencies to target areas for mosquito control activities and health education. WNV-infected mosquitoes have been identified across LA County with heightened risk in the San Fernando Valley, San Gabriel Valley and East Los Angeles. All county residents are encouraged to take protective action to prevent mosquito bites.

“We expect to see West Nile virus activity in mosquito populations through the fall,” said Truc Dever, General Manager for the Greater Los Angeles County Vector Control District. “It is, therefore, important that residents continue to take measures to protect themselves from mosquito bites and keep their yards mosquito-free. Be sure to use insect repellent with EPA-registered active ingredients when outdoors where mosquitoes are present and dump and drain standing water on your property. If you have any concerns or need to submit a service request, contact your local vector control agency.”

In 2015 in LA County, 300 human infections and 24 deaths due to WNV were reported. Most patients were older adults who experienced serious illnesses, such as meningitis and encephalitis. For many, recovery from their illness can take a year or more with ongoing physical and mental impairment. There is no specific treatment for this disease. In recent years, the peak month of onset of WNV illness has been September, and with cases continuing into November.

WNV is primarily spread to humans through the bite of an infected mosquito; mosquitoes can become infected by biting a bird that carries the virus. Most mosquitoes do not carry the virus and most people bitten by a mosquito are not exposed to the virus. The virus is not spread through person-to-person contact or directly from birds to humans.

WNV illness can be very severe, causing meningitis, encephalitis, paralysis, and death. Serious disease usually occurs in older adults and those with underlying medical conditions that reduce their immunity. These severe illnesses represent “the tip of the iceberg” with most infections resulting in no illness or mild symptoms that include fever, headache, nausea, body aches, and skin rash. Symptoms of WNV could appear within three to 12 days after infection.