West Nile Virus Activity in Montana

Montana public health officials have reported that eleven counties, including Cascade County, have had mosquito pools test positive for WNV in recent weeks. WNV usually follows a predictable course of infection in Montana with positive mosquito pools or birds detected, followed by cases in horses, and then in humans. The Department of Livestock recently announced that nine horses, in nine different counties, have tested positive for WNV. Cascade County has seen one case of equine WNV. One human case has been reported in the state. Public health officials are encouraging prevention measures in order to avoid any more human cases.

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. Follow the directions on the package. To learn more about choosing a repellent, click here.
  • 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.). Click here (attach residential control document from Elton) for more information about eliminating mosquitoes around your home.
  • Dress Appropriately – Wear long-sleeved shirts, long pants, and socks.

The symptoms and severity of WNV can vary widely. Approximately 80% of persons infected experience no symptoms; up to 20% can develop a mild illness, called West Nile fever. West Nile fever generally resolves itself without treatment, but dangerous brain infections, like encephalitis or meningitis, can develop in 1 out of 150 infected 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.

For more information on WNV, including how to prevent it, download our printable fact sheet or visit www.cdc.gov/westnile.