NORTHERN CALIFORNIA – California Department of Public Health Director and State Health Officer Dr. Karen Smith on Monday announced the first confirmed death in California due to West Nile virus.

The deceased person was a senior citizen in Nevada County.

“This death is a tragic reminder of how severe West Nile virus disease can be,” said Dr. Smith. “West Nile virus activity is more widespread in 2015 than in years past. Californians need to be vigilant in protecting themselves.”

West Nile virus is influenced by many factors such as climate, the number and types of birds and mosquitoes in an area, and the level of immunity in birds to the virus.

It is possible that the drought has contributed to West Nile virus amplification by reducing sources of water for birds and mosquitoes, state officials reported. As birds and mosquitoes seek water, they are coming into closer contact and amplifying the transmission of the virus.

Thirty-three California counties have reported West Nile virus activity so far this year, four more than this time last year and above the five-year average of 22, the state said.

To date, 497 mosquito samples have tested positive for West Nile virus, which exceeds the five-year average of 330, according to state health officials.

Lake County's first positive mosquito samples of the year were confirmed last week, as Lake County News has reported. Those samples were collected in Clearlake Oaks, Upper Lake and Kelseyville.

West Nile virus is transmitted to humans and animals by the bite of an infected mosquito.

The risk of serious illness to most people is low. However, some individuals – less than one percent – can develop a serious neurologic illness such as encephalitis or meningitis.

People 50 years of age and older have a higher chance of getting sick and are more likely to develop complications.

Studies also indicate that those with diabetes and/or hypertension are at greatest risk for serious illness.

The California Department of Public Health recommends that individuals prevent exposure to mosquito bites and West Nile virus by practicing the “Three Ds”:

– DEET: Apply insect repellent containing DEET, picaradin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children two months of age and older.

– DAWN AND DUSK: Mosquitoes bite in the early morning and evening so it is important to wear proper clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes.

– DRAIN: Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, by emptying flower pots, old car tires, buckets, and other containers. If you know of a swimming pool that is not being properly maintained, please contact your local mosquito and vector control agency.

California’s West Nile virus Web site, http://www.westnile.ca.gov/ , includes the latest information on West Nile virus activity in the state.

Californians are encouraged to report dead birds on the Web site or by calling toll-free 1-877-WNV-BIRD (968-2473).