LAKE COUNTY, Calif. – Lake County has reported its first probable case of West Nile virus and is investigating a second, which officials said serves as a reminder that this mosquito-borne disease is present and circulating.
“Even though our attention has been dominated by recent wildfires, we should not forget that West Nile Virus season is in full force,” said Lake County Health Officer Dr. Karen Tait. “Since there is no specific treatment once the infection develops, the best prevention is to avoid exposure through mosquito bites.”
West Nile Virus infection can range from mild, even symptom-free infections, to deadly forms of the disease. Mild forms of the infection often go undetected.
Less than 1 percent of cases result in severe illness and these are the most likely to be diagnosed. People over age 50 and diabetics are at risk for the more severe forms of the disease.
Local surveillance is a joint effort of Lake County Vector Control District and Lake County Public Health.
Typically, before human cases occur, the infection first appears in mosquito pools, followed by wild birds and sentinel chicken flocks selected for regular testing.
This pattern was the case this year, with the West Nile virus first noted in mosquitoes on July 9, a positive wild bird on July 24, and a positive sentinel chicken flock on July 27.
The first human case reported this year in Lake County became ill during the third week of July, officials said. The second probable case that remains under investigation became ill in mid-August.
Both individuals experienced the “neuroinvasive” form of the infection, which can produce symptoms ranging from a form of meningitis to more severe and potentially permanent effects on the nervous system.
Officials said both Lake County residents are making a good recovery.
Lake County Public Health and Lake County Vector Control District have a strong partnership for control of West Nile virus and other vector-borne diseases.
When Public Health receives a report of a suspected case, Vector Control is immediately informed and takes action to increase surveillance and reduce mosquitoes in the locations where the individual was likely to have been exposed.
“Even though we cannot always prevent a first case of West Nile virus, we have tools at our disposal to reduce the chance of additional cases in the same neighborhood,” said Tait.
Dr. Jamesina Scott, Vector Control district manager and research director, said the steps in response to reported West Nile virus activity include searching for sources of standing water where mosquitoes develop, which are often in the form of neglected ponds and swimming pools.
“We’re fortunate to have a close partnership with Public Health. When there is a suspected West Nile virus case, we are able to respond quickly to reduce the risk of additional human cases,” said Scott.
“With the drought, we’re seeing more swimming pools being taken out of service. When a pool isn’t being chlorinated or filtered, it becomes the perfect home for mosquitoes,” Scott explained. “We offer free mosquito-eating fish for use in unmaintained swimming pools – they eat the immature mosquitoes before they grow into flying, biting adult mosquitoes.”
Since 2004, six people in Lake County have been diagnosed with West Nile virus. For 2015, West Nile virus has been detected in 20 mosquito samples, three dead birds, and two sentinel chickens in Lake County.
So far this year in California, 57 human cases, including two fatalities, have been reported from 13 counties. More than one-third of the cases were reported in the past week.
In recent years, Lake County reported one case in 2012 and another in 2014.
How to prevent infection
Residents are urged to help reduce their risk of contracting mosquito-borne diseases by following these guidelines:
• Dump or drain standing water. Mosquitoes can't begin their lives without water. If the water cannot be drained (like an unused swimming pool), call Vector Control at 707-263-4770 for free mosquitofish.
• Defend yourself against mosquitoes by using repellents containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
• Avoid being outdoors when mosquitoes are present, typically dawn and dusk.
• Report neglected swimming pools by calling 707-263-4770 or visiting www.LCVCD.org . Anonymous calls accepted. Just one neglected pool can produce thousands of mosquitoes every day that affect people up to five miles away.
• Report dead birds to the state hotline: 1-877-968-2473. All reports are crucial, even if the bird does not meet criteria for testing.
Residents with questions, or who need help with a mosquito problem should contact the Lake County Vector Control District at 707-263-4770 or visit www.lcvcd.org .
For more information about West Nile virus, visit http://www.westnile.ca.gov/ .
Information about mosquito repellents can be found on the US Centers for Disease Control and Prevention Web site at http://www.cdc.gov/westnile/faq/repellent.html .