West Nile Virus in Columbia County

During the active mosquito season between June through September, we trap adult mosquitoes in different breeding sites around Columbia County. These trapped mosquitoes are then speciated and disease vectoring mosquitoes are sent for testing at Oregon State University Veterinary Diagnostic Lab in Corvallis. We test for only three (3) types of encephalitis: West Nile virus (WNV), St. Louis encephalitis (SLE), and Western Equine encephalitis (WEE) .

Human cases of Western equine encephalitis and St. Louis encephalitis virus have occurred in Oregon in the past. Most cases occurred in eastern Oregon locations. Most West Nile virus cases occur in the late summer and fall.

Below are any positive tests for West Nile virus:

2023 Season

No (0) positives.

Mosquito Pools	0
WNV Positive Mosquito Pools	0
Infected Birds	0
Infected Horses	0
Human Cases	0

Map of the 2023 season counties testing Positive for WNV. Download

Updated: 9/6/2023

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2020 Season

1 Positive West Nile virus samples from a human.

This positive WNv human case was a 59-year-old male, from Hankey road, St. Helens Oregon.

Mosquito Pools	0
WNV Positive Mosquito Pools	0
Infected Birds	0
Infected Horses	0
Human Cases (IgM +)	1

Map of the 2020 season counties testing Positive for WNV. Download

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2007 Season

2 Positive West Nile virus samples from Birds species (Aves)

Mosquito Pools	0
WNV Positive Mosquito Pools	0
Infected Birds	2
Infected Horses	0
Human Cases	0

Map of the 2007 season counties testing Positive for WNV. Download