The man, in his early 20's is the first person to be infected in Washington state.

Two other Western Washington residents have tested positive for the mosquito-borne virus, but likely contracted it out of state.

The Walla Walla confirmation was made by the Washington State Public Health Laboratory in Shoreline, WA.  The man has been treated at an area hospital.  Several additional suspected cases are being investigated.

Officials say 34 mosquito samples this year have tested positive for the virus,  11 each in Benton and Franklin counties, and 12 in Grant. The number of positive samples this year (34) has already surpassed the total of the last three years combined (28).

State Health officials stressed the need to prevent mosquitoes from hatching by making sure you avoid prolonged standing puddles or water near your home, removing excess garbage and weeds where water may develop. They also urge using repellent especially in evening hours, and make sure window screens are sufficient to keep insects out of your home.   From the Washington State Department of Health release Monday:

"Year after year, south central Washington has been a “hot spot” for the virus, with most in-state acquired human and animal cases having been exposed in this area. Mosquito testing shows the virus is in our state, and the mosquito species that transmit the virus are found throughout Washington. Regardless of where you are, health officials recommend avoiding mosquito bites to help prevent getting infected."

Most people who come in contact with the virus don't develop symptoms at all.  Some may develop fever, headache or body aches.   A small percentage of people can contract meningitis, encephalitis or other complications.  Infants and people over 50, especially those in poor health, are most at risk.

State health officials have been using aerial spraying around ponds and other bodies of water where positive tests have been recorded to help deter the spread of the insects.