PENDLETON, Ore. (AP) — The discovery of the West Nile virus in two counties in East Oregon has triggered a seek-and-destroy mission for adult mosquitoes in the 274 square-mile North Morrow Vector Control District.

The East Oregonian reports (http://bit.ly/U22w2U ) surveillance is conducted on problem areas weekly, which are then treated with pesticide.

Two August discoveries of the virus touched off the decision to seek adult mosquitoes. The control district usually focuses on eliminating mosquito larva.

Traps armed with dry ice produce carbon dioxide, attracting mosquitoes into a net, where they are held until their species can be identified.

Only certain species can carry West Nile, so disease-carrying species are sent to the Oregon State University Veterinary Diagnostic Lab for testing.

The last time the virus infected the area was in 2009.

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Information from: East Oregonian, http://www.eastoregonian.info