PORTLAND (AP) - Oregon's brush with the West Nile virus last summer might have been merely a primer for what the state will face this year, a health official said.

The mosquito-borne virus, which has been detected in eight counties, sickened birds, horses and five people last year. This year, hundreds of human cases could be diagnosed if the virus follows the pattern seen in other states, said Emilio DeBess, a public health veterinarian and epidemiologist with the Oregon Department of Human Services.

DeBess will convene a summit March 8 in Portland for public health and hospital officials from across the state to plan how to deal with a major outbreak.

The virus, which peaks during the summer when mosquitoes are most active, entered the United States in New York in 1999 and has moved clear across the country. It killed 88 people in 2004, according to the national Centers for Disease Control and Prevention.

DeBess and other epidemiologists theorize that the disease can enter an area in three stages. In the beginning stage, infected birds fly into a state and are bitten by mosquitoes, which in turn become infected with the virus.

During the second stage, the virus spreads widely among mosquitoes. The mosquitoes bite a large number of people who become infected. DeBess said it is likely that Oregon is entering the second stage and will see substantial numbers of human infections this year.

In the third year and beyond, the number of human cases typically declines rapidly because those who were previously exposed to the virus acquire an immunity to it.

Colorado, for example, appears to have followed this path. It reported 14 human cases in 2002. That ballooned to 2,947 in 2003 and then dwindled to 276 last year.

DeBess said that although the number of human cases goes down in subsequent years, the amount of virus circulating among mosquitoes is still high.

"The thing to remember is that the virus circulates between birds and mosquitoes," DeBess said. "Human beings are dead-end hosts. They're just innocent bystanders in this."