One of the simplest ways to avoid transmitting cold and flu bugs is to wash your hands. No soap and water nearby? Hand sanitizer is a good second choice.
Travel can hamper efforts to wash hands. The majority of flu is transmitted hand-to-hand or skin-to-skin, so it’s important to wash your hands frequently. Ironically, just when travelers are particularly susceptible to respiratory illnesses due to close contact with a lot of people carrying cold and flu bugs, hand-washing becomes less convenient due to lack of facilities. During winter travel, large family gatherings, hugs, and handshakes all provide ample opportunity for the flu virus to spread. If you can’t wash your hands thoroughly several times a day, rely on winter gloves when reasonable. More importantly, avoiding rubbing your eyes or nose.