"Throughout the U.S., once a county is identified with the virus, and once that virus gets into an area, it's there to stay," said John Townsend, vector control manager for Maricopa County Environmental Service Department. "Every year from now on, Arizona and Maricopa County are going to have to deal with the virus."

The samples were collected in late September at 13 locations, mostly in Chandler, but also in Gilbert, Mesa and Phoenix. Results came back Tuesday, according to Jeanene Fowler, spokeswoman for the county environment services department.

The department conducts routine testing for the virus all over the county, but decided to focus on the East Valley after a dead chicken in Chandler tested positive a few weeks ago.

"This doesn't mean that the East Valley is a hotspot, it just means that we've done more testing in that area after the chicken in Chandler tested positive for West Nile," Fowler said.

But with only four weeks of mosquito season left, the department isn't taking any new steps or precautions until next year. "We still continue to conduct tests every week," Fowler said. "The biggest thing people can do is in their back yard." Fowler said eliminating stagnant water in backyards is the best action residents can take to prevent the spread of the disease.

West Nile is a mosquito-borne virus that causes mostly mild or no symptoms in the majority of people who contract the virus.

But it can cause more serious conditions, such as an inflammation of the brain and brain lining - known as encephalitis - and even death. The elderly and those with compromised immune systems are most susceptible. One human death has been reported this year in Arizona. A Graham County man died after contracting the disease while visiting Colorado or Wyoming, officials said.

The second year for the virus is almost always the worst, according to Townsend.  "And next summer will be our second with West Nile," he said. Human deaths may follow, but probably not until late into the summer and early fall, Townsend said
"Early in the summer, only birds and mosquitoes pass the virus back and forth to each other," he said. "Later into the summer you may get horses and humans when the mosquito population has become inflamed." Fowler likened next summer in Arizona to Colorado this year, where 36 people have died from the virus.The department will be gearing up in advance of next summer to offer outreach programs aimed at educating residents, especially the elderly, about the virus and its risks. 

For more information on the virus, visit www.maricopa.gov/envsvc or http://www.cdc.gov/ncidod/dvbid/westnile/.