The U.S. Chamber of Commerce on Friday offered companies new guidelines for coping with the H1N1 swine flu pandemic, warning that employers could face crippling absenteeism as the U.S. flu season takes hold.

In the 16-page volume titled, It's Not Flu as Usual: An H1N1 Business Preparedness Guide, the largest American business federation presented scenarios in which more than 10 percent of staff are too sick to come to work on any given day over the course of several months to a year.

Absenteeism will be the central issue that businesses wrestle with during this pandemic, said Ann Beauchesne, who leads the chamber's national security and emergency preparedness program.

The chamber acknowledged that influenza rates and absenteeism are difficult to predict but said business owners and corporate executives need to be aware of how bad the situation could become.

Seasonal flu kills about 36,000 people each year in the United States, hospitalizes more than 200,000 and costs more than $10 billion in direct medical expenses and lost productivity.

H1N1 flu does not appear to be any more deadly but is expected to infect more people than seasonal flu does because so few people have any immunity to it. It is also expected to affect younger people more than does seasonal flu, including young and middle-aged adults, as well as their children.

In communities where H1N1 flu circulated this past spring, the infection rate was roughly 6 percent to 8 percent over a three- to four-week period. During the winter season, infection rates could be two to three times higher, as both the H1N1 (swine) flu and the seasonal flu circulate and sicken people simultaneously, the guide said.

The chamber, which represents more than 3 million businesses and organizations, said it has been collaborating closely with the U.S. government to help its members weather the H1N1 pandemic, expected to worsen in the Northern Hemisphere as cooler autumn temperatures set in.

The guide offers a 10-point checklist that urges companies to encourage sick workers to stay home, maintain healthy air circulation, promote hand-washing and plan for interruptions in government services including sanitation, water, power, transportation and food distribution.

The chamber also included a list of Internet Web sites, including, which contain detailed information on topics like federal guidance for workplace planning, vaccines, antiviral drugs, face masks, and respirators.