The Los Angeles County Department of Public Health (Public Health) has identified the first case of human West Nile virus (WNV) infection in Los Angeles County for the 2017 season (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments). An elderly resident of the San Gabriel Valley region of Los Angeles County was hospitalized in late March and West Nile virus was recently confirmed as the cause by the California Department of Public Health. The patient has since recovered.
“West Nile is a serious illness spread by mosquitoes in Los Angeles County. Take precautions against mosquito bites such as using a repellent containing DEET when outdoors, especially around dawn or dusk,” said Jeffrey Gunzenhauser, MD, MPH, Interim Health Officer for Los Angeles County. “There is currently no vaccine or treatment for West Nile virus. Elderly persons and other people with weak immune systems are at highest risk of developing severe illness.”
WNV is a leading cause of severe infections of the nervous system among adults older than age 50 in Los Angeles County. It can cause meningitis, encephalitis, and paralysis. In 2016, during the mosquito season in the summer and fall, there were 153 cases and 5 deaths from WNV infection reported to Public Health. Of the 153 West Nile cases reported in 2016, there were 48 residents with meningitis, 53 residents with encephalitis, and 5 residents with paralysis. People most at risk of WNV include elderly people who are often outside walking or gardening when they can be bitten by a mosquito and people whose immunity is compromised because of illness or medications they take.
Public Health tracks WNV and other arboviral disease cases (e.g. Zika virus) and collaborates with local vector control agencies to target areas for mosquito control activities as well as educate people about how to protect themselves.
“It is an unfortunate fact that West Nile virus will continue to impact the health and wellbeing of our residents. However, we can take steps to lessen the impact of the disease. Through vigilant detection and suppression of mosquito breeding sources by both vector control agencies and community members, we can help keep disease transmission to the lowest level possible. Residents are reminded to conduct weekly property inspections, and dump or drain any standing water found.” said Jared Dever, District Manager of the San Gabriel Valley Mosquito and Vector Control District.
WNV is spread to humans through the bite of an infected mosquito; mosquitoes 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 WNV. The virus is not spread through person- to-person contact or directly from birds to humans.
Most WNV infections reported to public health are severe. Recovery from WNV can take months or years. One study showed that 12 months after infection, about half of those with this disease continued to have cognitive and physical impairment such as memory loss, difficulty walking and fatigue. In addition to those who develop more serious illness, people infected with West Nile virus may develop mild symptoms that include fever, headache, nausea, body aches, and a mild skin rash.