The person was only identified as a resident of the eastern region of the county. The patient was hospitalized and died from West Nile virus-associated neuro-invasive disease, the county's public health department said in a news release.
"To the family and friends feeling the sorrow of losing this person due to WNV, we send you our deepest sympathies," said L.A. County Health Officer Muntu Davis in a statement. "West Nile virus can be a serious health threat to people who get infected."
West Nile virus is spread by mosquitoes, and is a recurring problem in Southern California, particularly in the summer.
Symptoms may include fever, headache, nausea, body aches and a mild skin rash. Officials remind residents to try to clear any standing water from around the home as it can attract mosquitoes, and to put on insect repellent when outside and when mosquitoes are present.
"People should regularly check for items that can hold water and breed mosquitoes, both inside and outside their homes, and to cover, clean or throw out those items," Davis said. "I encourage everyone to protect themselves from diseases spread by mosquitoes by using EPA-registered mosquito repellent products as directed, and wear clothing that covers your arms and legs."
Health officials say people over 50 and those with chronic medical conditions, such as cancer and diabetes, can develop severe infection. There is no vaccine for the virus.
Ten cases of West Nile virus have been reported in L.A. County this year, excluding Long Beach and Pasadena as those cities have their own health departments.
City News Service contributed to this report.