As many as two out of five Oregonians are expected to come down with the flu this fall and winter, prompting the state to prepare for the possibility of an epidemic that would close schools and threaten the economy, officials said Friday.

SALEM — As many as two out of five Oregonians are expected to come down with the flu this fall and winter, prompting the state to prepare for the possibility of an epidemic that would close schools and threaten the economy, officials said Friday.

One of the top concerns is a possible outbreak of the H1N1 flu virus, commonly called swine flu, which has been blamed for nearly 500 deaths nationally since the start of the last flu season, including 11 in Oregon.

Gov. Ted Kulongoski opened a statewide summit on the flu threat Friday in Salem with a plea to Oregonians to be ready to take care of themselves at home to avoid straining limited health care resources during a major outbreak.

“Families and communities have to develop plans to be able to take care of themselves,” Kulongoski said. “If you expect the government to be there for every single family, it’s not possible.”

He also said the state is urging companies and small business owners to encourage employees to stay home if they come down with the flu to prevent its spread.

“If you have 40 percent of the work force of the state at some time in the next six to eight months coming down with the flu, you’re going to substantially impact our productivity and our ability to recover from the current economic crisis, so this is very, very serious,” Kulongoski said during a news conference at the summit.

But the governor made clear that help will be available from state and federal agencies which will respond at whatever level necessary to battle an outbreak or an epidemic, including assistance from the Oregon National Guard.

Dr. Mel Kohn, the state public health director, said the state developed a good relationship with its federal partners during the last flu season and he expects strong cooperation between schools, county health agencies and hospitals in Oregon.

“I think that ultimately the responsibility for protecting public health is a state responsibility,” Kohn said. “But there are tremendous resources at the federal level.”

Health officials say infections from swine flu, like the seasonal flu, can range from mild to severe. Symptoms are a high fever, cough, sore throat, chills, body aches and fatigue.

The H1N1 strain of the type A influenza virus appeared in the United States in late March and quickly spread across the country and the world before it was declared a pandemic by the World Health Organization in June.

More than 800 people attended the summit, representing schools, state and county emergency managers, hospitals and businesses.