Samples Test Positive for West Nile Virus in Jackson County

West Nile virus has been detected in mosquitoes collected east of White City, Oregon on August 18th, 2020.  “Oregon State University Veterinary Diagnostic Laboratory in Corvallis confirmed the positive mosquito pools,” said Geoff Taylor, Manager of the Jackson County Vector Control District. 

Taylor explained that the Jackson County Vector Control District routinely sets 48 dry ice baited adult mosquito traps weekly throughout Jackson County.  The mosquitoes caught are then identified by species, counted, and pooled into groups of 10-50 and sent to the OSU Veterinary Diagnostic Laboratory in Corvallis for testing. The District has tested 285 pools since June this year for West Nile virus, Saint Louis Encephalitis, and Western Equine Encephalitis, one of which was positive for West Nile virus.    

West Nile virus has been previously detected in Jackson County during the 2005, 2006, 2007, 2008, 2012, 2013, 2014 and 2015 mosquito seasons.  The August 18th mosquito pool brings the total to one confirmed West Nile virus positive pool this season in Jackson County.  To date there has been one West Nile virus reported in Jackson County.  The last known human case of West Nile Virus in Jackson County was in 2005. 

Dead bird surveillance has been ongoing in the district.  “People that notice sick or dead birds such as crows, ravens, jays or robins should contact the vector control district at 541-826-2199 so that they can be picked up for testing,” Taylor said. 

“Most people who become infected with West Nile virus do not become sick.  Some may develop mild flu-like symptoms such as fever, headache, body aches, and occasionally swollen lymph glands or rash.  In some cases, West Nile may cause encephalitis, or inflammation of the brain,” said Jackson Baures, Jackson County Public Health Division Manager, “individuals with severe or unusual headaches should seek medical care as soon as possible.” West Nile is spread to humans through the bite of an infected mosquito.  Most infected people will show little or no signs of disease.  About 1 in 5 infected people may show signs of West Nile fever. People at risk include those individuals over 50 years of age, people with immune compromising conditions, or those people with diabetes and high blood pressure. Symptoms may include fever above 100ºF AND severe headache, stiff neck, mental confusion, muscle weakness, shaking, paralysis, or rash. It is important that you contact your health care provider if you experience any of these symptoms. The fever syndrome may last from a few days to several weeks.  The incubation period is usually 2-14 days.

The staff at the Jackson County Vector Control District has increased surveillance and control measures within the district in response to the increased public health threat. 

“With warm temperatures expected the rest of this week, we encourage people to take appropriate precautions to protect themselves from mosquito bites,” said Taylor.  He offered the following suggestions to reduce the risk of exposure to West Nile virus:

  • Eliminate all sources of standing water that can be a breeding ground for biting mosquitoes, such as flooded fields, watering troughs, birdbaths, wading pools, clogged gutters and old tires. If it holds water for 7 days, it can produce mosquitoes.
  • Stock water troughs and ornamental ponds with mosquito fish, available free at the District Office.
  • Avoid outdoor activities at dusk and dawn when mosquitoes are most active.
  • Wear long-sleeved shirts and long pants when in mosquito infested areas. 
  • Use mosquito repellents containing DEET, Oil of Lemon Eucalyptus, IR3535 or Picaridin, making sure to follow the directions on the container. 
  • Make sure all screen doors and windows are in good repair and fit tightly. 

Additional information on West Nile Virus is on the Web at:

U.S. Centers for Disease Control and Prevention

Oregon Public Health Division