The national flu outbreak is doing more than making people sick. It's hurting worker productivity and businesses across the country are ailing from increased healthcare costs and widespread absenteeism, says John Challenger, CEO of Challenger, Gray & Christmas, an outplacement consulting firm.

Sick employees may be worried about job security or are eager to continue contributing to their workplace, but "presenteeism," or when workers perform at reduced capacity, only makes matters worse by spreading illnesses, he advises.

"The economy is still on shaky ground and many workers continue to be worried about losing their jobs, despite the fact that annual layoffs are at the lowest level since the late 1990s," Challenger says. "In this environment, workers are reluctant to call in sick or even use vacation days."

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The cost of the flu to businesses may be significantly higher this year, as this season's flu outbreak is particularly severe.

We're now entering the worst part of the flu season, Challenger warns. “Companies that may already be shorthanded coming out of the recession could find themselves struggling to keep up with demand in the weeks ahead as absenteeism claims more manpower.”

Businesses should let sick workers stay home without fear of losing their jobs, he suggests. In addition, companies should also increase telecommuting, enforce strict hygiene practices, increase the number of shifts, limit meetings and conduct more meetings via conference calls.

The flu outbreak is indeed severe. Most of the country is experiencing high levels of influenza-like illness, according to the Centers for Disease Control and Prevention.

“Anyone who has not already been vaccinated should do so now,” says Dr. Joe Bresee, chief of the Epidemiology and Prevention Branch in CDC’s Influenza Division.

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