Hospital beds set up in gymnasiums. Retired nurses called in to work. Non-urgent surgeries postponed.

It's a worst-case scenario local hospitals say they're ready to deploy if massive flu outbreaks become the next big test of the health care system.

By some estimates, the H1N1 virus (known as swine flu) could infect up to 40 percent of the U.S. population, or double the rate of the typical flu. While most people should experience only mild or moderate symptoms, hospitals expect to be overwhelmed.

Swine flu is only the latest challenge to hospital preparedness. Disaster planning ramped up nationwide after Hurricane Katrina uncovered deadly holes in New Orleans' hospital system.

St. Louis' own hospital system has been tested since. In 2006, ice storms and power outages crowded hospitals with residents of nursing homes that lacked generators.

Then the winter of 2007-2008 brought the worst flu season in more than 30 years. Emergency room wait times reached five hours as cots were lined up in hospital hallways. At the peak of the outbreak, 15 hospitals were turning ambulances away.

This flu season could be worse, if the seasonal flu shows up as usual in December or January and the swine flu is still circulating.

To prepare for the unusual flu season, hospitals have stocked up on masks and gloves. They've reserved emergency ventilators with rental companies. Staff have practiced surge capacity drills.

"I think that we're more prepared than we were a couple years ago," said Dr. Hilary Babcock, medical director of occupational health at Barnes-Jewish and St. Louis Children's hospitals. "The hospitals reviewed their pandemic planning policies and ran drills to test and stress those policies to see if they would work in a true surge."

Officials at Barnes-Jewish and other hospitals say they are prepared to postpone elective surgeries to open up more beds for flu patients. Forest Park Hospital has devoted one section to treat people with flu and keep them isolated from the general patient population.

And hospitals say they're prepared to work together. Some might open up beds to take overflow from neighboring hospitals, or trade ventilators as needed.

"We think we can handle a surge, and we're ready to share with other hospitals," said Dr. Robert Griesbaum, vice president of patient care quality at St. Anthony's Medical Center.

One way to keep hospitals humming along is to make sure health care workers don't get sick.

Nurses in one out of five hospitals have been infected with swine flu, according to a California Nurses Association survey of 190 hospitals in nine states, including Illinois.

Historically, health care workers have a poor record of getting flu vaccinations, with national estimates of about 40 percent. This year, people will need to receive at least two sets of shots to be protected from swine and seasonal flu.

The two largest local hospital systems, BJC HealthCare and SSM Health Care, now require all employees to get the seasonal flu shot with few exemptions. Many hospitals have already started offering the vaccines free to staff this year.

"Protecting health care workers is critically important," said Dr. Thomas Frieden, director of the federal Centers for Disease Control and Prevention, in a recent conference call with reporters. "They are the first line of defense."

That's why health care workers will be among the first to receive the swine flu vaccine when it becomes available as expected in mid-October. Expecting a public rush on the vaccine, the St. Charles County health department put out a call for volunteers to help run immunization clinics.

Perhaps the biggest challenge for health departments and hospitals is educating the public on the new virus that has garnered a lot of attention and concern.

So far, the swine flu has not proved to be more deadly than the flu viruses that circulate each winter.

More than 1 million Americans are thought to have been infected with swine flu and nearly 600 have died. In a typical season, up to 60 million become infected with flu and 36,000 die of complications.

The best place to treat either flu, experts say, is at home.

Emergency room and doctors' visits should be reserved for people with trouble breathing, chest pain or severe dehydration. But people with underlying conditions such as heart disease, diabetes, asthma or pregnancy should seek care if they develop a fever.

It's a complicated message, but important to understand so hospitals can stay open for the people who really need them, Frieden said.

"For most people with the flu, there's no reason to see a doctor or go to the emergency department unless you're severely ill," he said. "The overwhelming majority of people with H1N1 influenza are going to do fine."