Your phone, keyboard and desktop are most likely a health hazard. Breathing into your phone, holding your handset, scratching your nose or some other part of your body then typing on your keyboard can transmit germs to each surface. Then when a colleague uses your phone, you're sharing more than office equipment. Make wipes available for employees to wipe down their desktop areas.
Promote the germ-free zone
Things touched by many, such as door handles and bathroom taps, are major sources of germs. Strategically placed hand sanitisers at places such as reception, board rooms, conference areas and anywhere else people congregate will help.
Vaccinations
Sometimes it's hard for people to organise their own flu shots. But many providers will come to your office to provide vaccinations for your staff during work time, saving time and money. Consider the payment for vaccinations for your staff an investment in their productivity this winter. Organising an hour for shots for your team will be better than having them off for a week.
Don't encourage staff to tough it out
If your staff are obviously sick, send them home. "Presenteeism", or working through sickness, can be just as bad for productivity and is also a risk to the rest of your staff.
Encourage a culture where staff feel able to take the leave they need and where you don't have to worry that anyone is taking advantage of it.
Being a boss doesn't mean you need to enforce a strict routine over every person you have enter the office. Rather, encourage discussion around the things that might need to change in your workplace for a healthy environment through the winter season.