All those signs advertising the availability of flu shots? They're a harbinger of winter and a reminder to all companies that increasing levels of employee absenteeism and presenteeism are right around the corner. When team members aren't feeling well, they can't perform at their highest levels, which means significant hours of lost productivity.

Just how much do down-for-the-count personnel affect the average company's bottom line? The Virgin Pulse Global Challenge surveyed 5,500 organizations in 185 countries and found that absenteeism in the U.S., the U.K., and Australia alone costs organizations $150 billion each year. The study's findings also suggest that when workers show up despite feeling unwell, they don't exactly contribute to the whole. Presenteeism costs companies in those three countries $1.5 trillion each year. Considering that Gallup estimates that most American companies only work at 33% possible efficiency on their best days, businesses can hardly afford to lose more productive capacity.

In other words, having healthy employees should be everyone's goal. Although no employer can completely prevent workers from succumbing to illness, business leaders can at least make sure the workplace isn't contributing to the problem. After all, plenty of corporate environments unintentionally foster the incubation and spread of viruses and colds.

Want to do better by your workers? Here are three strategies to ensure your workplace remains a healthy, productive space.

1. Take a stress check.

Anyone who has been under tremendous mental pressure for weeks or months can start to exhibit physical symptoms, not to mention a lowered immune system. Chronic headaches, weight loss, gastrointestinal distress, mental fuzziness, and recurring colds tend to go along with long-term periods of stress.

Instead of allowing the stressors of work to eat away at the well-being of your employees, look for burnout signs, such as missed deadlines or careless work, and then do something before stress reaches epidemic proportions. There are a number of ways you can help employees find a little relief. Simply hosting meditation or yoga workshops can give your people much-needed breaks, while teaching the value of self-care.

Other suggestions to relieve office stress include being open to more flexible working arrangements and letting people occasionally leave early. "Find ways you can offer your employees flexibility that works for your business, advises Maria Haggerty, CEO of Dotcom Distribution. "We let our employees get a head start on the weekend by leaving early on Fridays in the summer when the work pace naturally slows down a little."

2. Encourage workers to use sick leave.

Our nation tends to laud sick employees who drag themselves into their seats. Yet all their efforts do is potentially expose everyone around to whatever illness they have. The Centers for Disease Control and Prevention recommend that anyone with a fever remain at home for 24 hours after it breaks. Besides, listening to co-workers sneeze and wheeze is a distraction.

Encourage ill workers to get the necessary rest. This doesn't mean they have to unplug entirely, of course. Laptops and smartphones make it simple to occasionally check-in. If your company hasn't adequately structured its sick leave policy, consider a revamp. For example, don't lump sick time into paid time off because it discourages people from prioritizing their health.

Your objective shouldn't be to have all hands on deck if one of your employees can give only 15% at most. Be vocal about your expectations that sick workers notify the right people and take the time they need to recover.

3. Stay on top of tidiness.

An unclean workspace is a bacterial breeding ground. That's why you should make antibacterial wipes, sprays, and other cleaning solutions available to workers. That way, they can quickly tend to areas that receive the most traffic. Public office spaces that receive lots of visitors, such as banks, are especially prone to all sorts of germs.

"Three spaces deserve your immediate attention: restrooms, teller stations, and glass surfaces," explains Stephen Lewis, technical director of milliCare Floor & Textile Care. "Empower your personnel ... to use sanitizing wipes between customers to minimize germs and dirt."

That's good advice for any workplace, not just banks. At the same time, think beyond the desk areas. Keep up with HVAC maintenance, and remember that simply replacing the filters in your vent system can improve indoor air quality and tamp down on airborne allergens.

Sickness happens to the best of us, and it's going to happen in your workplace this year. But you can take steps to ensure your employees are prioritizing their health and responding appropriately when they're ill. Examine your company policies and communicate your expectations early. That way, you can beat the bugs at their own game.