Los Angeles health officials urge public to take preventative measures against West Nile virus

Apr 24 2004

Los Angeles health officials have issued a statement urging the public to take precautions against mosquitoes after crows in the county tested positive for the West Nile virus. "These findings are a clear warning that the virus is continuing to circulate and amplify in the environment. Now is the time to take precautions," said Steve West of the San Gabriel Valley Mosquito and Vector Control District.

The detection of West Nile virus (WNV) in Los Angeles and Orange counties marks the first evidence of the virus in California this year, State Health Director Sandra Shewry announced today. In Los Angeles County, the virus was confirmed Thursday in a dead crow collected from the San Gabriel Valley. Orange County vector control and health officials announced yesterday that antibodies to WNV were detected in two local house finches.

"West Nile virus has been detected earlier than expected this year, probably due to unseasonably warm weather," Shewry said. "The state's surveillance system is closely monitoring for any evidence of the virus across the state. West Nile virus infection has not been detected in humans this year."

The state's interagency surveillance system for WNV includes testing of dead birds, mosquitoes and sentinel chickens. The dead bird surveillance program is coordinated by the California Department of Health Services (CDHS). The WNV positive dead crow was reported to CDHS by a resident on Feb. 24 and picked up by the San Gabriel Valley Mosquito and Vector Control District. The crow was shipped to the California Animal Health and Food Safety Laboratory for initial processing before being tested at the University of California, Davis, arbovirus diagnostic laboratory. Test results were confirmed today.

Shewry encouraged the public to report birds that have been dead for less than 48 hours to CDHS’ toll-free hotline: 1-877-WNV-BIRD. The public can report dead crows, ravens, magpies, jays, sparrows, finches and raptors to the hotline. Individuals should take note of the bird’s location and its condition before calling for further instructions, including assistance with identifying the type of bird found. The bird should show no signs of decomposition or maggot infestation. While there is no evidence that people can get the virus from handling live or dead infected birds, individuals should not attempt to catch or handle them. "We are calling on the public to provide us with information about dead birds so we can detect movement of the virus in order to protect the public health," she said.

In 2003, WNV was detected in dead birds, mosquitoes, sentinel chickens and a horse from six southern California counties. Three human WNV cases were detected in residents from Imperial, Riverside and Los Angeles counties. At this point in the year, 161 dead birds and 170 pools of mosquitoes have been tested for WNV infection. More than 230 flocks of sentinel chickens will be stationed throughout California this month. The chickens will be tested every other week through October to monitor WNV activity. To date, WNV infection has not been detected in mosquitoes or horses. Nationwide in 2003, WNV was linked to a total of 9,389 illnesses and 246 deaths. Since it was first detected in the United States in New York in 1999, WNV has been found in 46 states and the District of Columbia. Most individuals who are infected with WNV will not experience any illness. Others will have mild to moderate symptoms, such as fever, headache and body aches. Less than one percent of individuals will develop serious neurologic illness such as encephalitis and meningitis. The elderly and those with lowered immune systems are more susceptible to serious illness. WNV is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds. Human-to-human transmission of WNV generally does not occur. However, human WNV infection was associated with blood transfusions and organ transplants in 2002. Individuals can reduce their risk of mosquito-borne diseases by taking these precautions:

• Avoid spending time outside when mosquitoes are most active, especially at dawn and dusk.
• When outdoors, wear long pants and long-sleeved shirts.
• Apply insect repellent according to label instructions.
• Make sure that doors and windows have tight-fitting screens. Repair or replace screens that have tears or holes.
• Eliminate all sources of standing water on your property that can support mosquito breeding.
• Contact your local mosquito and vector control agency if there is a significant mosquito problem where you live or work.

The comprehensive surveillance program to monitor for WNV in California has been established by CDHS in collaboration with the University of California, Davis, California Department of Food and Agriculture, local mosquito and vector control districts and other state and local agencies. Since horses are susceptible to WNV and a vaccine is available for horses, horse owners are advised to contact their veterinarians about timely vaccinations. For more information about WNV or to report dead birds, visit the Web site http://www.westnile.ca.gov/.

Last year almost 10,000 people nationwide were infected and some 260 people died from the virus. Health experts say the best protection is to avoid mosquito bites by staying indoors from dusk to dawn and wearing long sleeves and trousers when outside.

West Nile virus is a newly emergent virus of the family Flaviviridae, found in both tropical and temperate regions. It mainly infects birds, but is also the cause of a number of conditions in humans, horses, and some other mammals. It is transmitted by bites of infected mosquitoes.