First West Nile Virus Positive Mosquito Pool Detected

The Cascade County Weed & Mosquito Division has detected its first West Nile Virus (WNV) positive mosquito pool in 2014.  The first WNV positive sample of Culex tarsalis was collected north of Great Falls on Wednesday, July 16, 2014 and was confirmed by the lab at the Montana Department of Public Health and Human Services (DPHHS) on Thursday, July 17, 2014.

Will Patterson, Manager for the Division reassures residents, “the Cascade County Weed & Mosquito Division will continue to collect and test mosquito samples from its surveillance traps until the end of September to ensure we are taking all possible steps to help protect residents from WNV.”  Trixie Smith, Prevention Services Division Manager for CCHD, adds, “no infection in humans, horses, or birds, has been detected in Cascade County so far this year, but we still encourage all residents to take steps to protect themselves.”

The severity and symptoms of WNV can vary widely.  Approximately 80% of persons infected experience no symptoms, but up to 20% of persons can develop a mild illness, called West Nile fever.  West Nile fever generally resolves itself without treatment, but dangerous brain infections such as encephalitis or meningitis can develop in 1 out of 150 people.  Symptoms of these diseases might include headache, rash, high fever, stiff neck, mental confusion, muscle weakness, tremors, convulsions, coma, and paralysis.  Individuals who develop any of these symptoms should see their healthcare provider immediately.

The single best defense against WNV is bite prevention. To protect yourself, use the 4 Ds:

  • DEET-Apply repellent containing an EPA-registered active ingredient, such as DEET, and follow the directions on the package.
  • DUSK and DAWN-This is when mosquitoes are most active. Try to avoid outdoor activities during these times.
  • DRAIN STANDING WATER-Standing water is the perfect breeding ground for mosquitoes. Drain such areas around your home (gutters, pools, tires, buckets, water bowls, etc.).
  • DRESS APPROPRIATELY-Wear long-sleeved shirts, long pants, and socks.

For more information, download our printable fact sheet or visit the DPHHS website at