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Mosquitoes Test Positive for West Nile Virus

MOSQUITOES IN LAKE COUNTY TEST POSITIVE FOR WEST NILE VIRUS

LAKEPORT, Calif. – Two mosquito samples collected in Lake County tested positive for West Nile virus (WNV) this week.  The mosquitoes, Culex tarsalis (western encephalitis mosquito), were collected near Upper Lake August 9 and August 14.  

“The smoke and wildfires don’t affect West Nile virus,” said Jamesina Scott, Ph.D., District Manager and Research Director of the Lake County Vector Control District.  “Despite the smoky air, mosquitoes are still biting.”  

“If you plan to be outside when mosquitoes are active, use insect repellent applied according the directions on the label and reapply as directed,” urges Erin Gustafson, Lake County Deputy Health Officer. Dr. Gustafson also encourages residents, “Wear long pants and long sleeves, and residents can treat items, such as boots, pants, socks, and tents, with permethrin or buy permethrin-treated clothing and gear. Residents should also sleep under a mosquito bed net if air conditioned or screened rooms are not available or if sleeping outdoors.”

The District encourages residents to reduce their risk of contracting West Nile virus and other mosquito-borne diseases by:

  • Dumping or draining standing water to prevent mosquitoes.  Mosquitoes need water to complete their life cycle.
  • Defending yourself.  Use repellents containing DEET, Picaridin, IR3535, or Oil of Lemon Eucalyptus.  Follow the label directions.
  • Avoiding the outdoors when mosquitoes are present, typically dawn and dusk

So far this year, West Nile virus activity has been detected in four mosquito samples in Lake County.  Statewide, 33 California counties have detected WNV this year, mainly in mosquitoes.  Nineteen human cases of West Nile virus illness have been reported in California residents this year.  

Most people (80%) with West Nile virus do not develop any symptoms. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint, pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months. About 1 in 150 people infected with West Nile virus will develop severe illness which causes inflammation of the membranes that surround the brain and spinal cord. Symptoms of severe illness include high fever, headache, neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. Recovery from severe illness can take several weeks or months. Some effects to the central nervous system (brain and spinal cord) might be permanent. In about 1 out of 10 people who develop severe illness affecting the central nervous system, the infection can be fatal.  People over age 60 and those with certain medical conditions, such as diabetes, cancer, hypertension, kidney disease, and people have received organ transplants are at greatest risk of severe disease.  The most recent confirmed case of WNV infection in Lake County was in 2016.  

Serious symptoms in a few people. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

  • Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.
  • Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
  • Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.
  • About 1 out of 10  people who develop severe illness affecting the central nervous system die.
Diagnosis
  • See your healthcare provider if you develop the symptoms described above.
  • Your healthcare provider can order tests to look for West Nile virus infection.
  • To learn more about testing, visit our Healthcare Providers page.
Treatment
  • No vaccine or specific antiviral treatments for West Nile virus infection are available.
  • Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms
  • In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.
  • If you think you or a family member might have West Nile virus disease, talk with your health care provider.
  • To learn more about treatment, visit our Healthcare Providers page.
Mosquitoes that transmit WNV develop in the water in out-of-service swimming pools and spas, animal watering troughs, ornamental ponds, rain barrels, and other sources of standing water.  Residents can get mosquito-eating fish for these sources free of charge from the District.  Swimming pools and spas that aren’t being maintained can produce thousands of biting mosquitoes every day.  Residents can help reduce mosquitoes in their neighborhoods by reporting unmaintained pools to the District, Dr. Scott recommends.  

Residents with questions or who would like help with a mosquito problem, including reporting a neglected pool or spa, should contact the Lake County Vector Control District at (707) 263-4770 or visit their website at 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 website at http://www.cdc.gov/westnile/faq/repellent.html.

 

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