It varies, depending partly on where the germ-laden droplets fall. Experiments with specific cold and flu germs have shown potential survival times ranging from a few minutes to 48 hours or more. How long such germs remain capable of infecting you in day-to-day life is harder to say.
According to Dr. Steckelberg of the Mayo Clinic, Researchers have repeatedly found that cold and flu germs generally remain active longer on stainless steel, plastic and similar hard surfaces than on fabric and other soft surfaces. On any surface, though, flu viruses seem to live longer than cold viruses do. Other factors, such as the amount of virus deposited on a surface and the temperature and humidity of the environment, also have effects on how long cold and flu germs stay active outside the body.
The rapid spread of some colds and types of flu certainly suggests that indirect transmission is common. You might, for example, catch the flu or a cold from rubbing your nose after handling an object an infected person christened with a sneeze a few moments ago. That said, it's important to note that cold and flu viruses primarily spread when an uninfected person has direct contact — a handshake, for example — with an infected person.
This is the height of flu season. The best way to avoid becoming infected with a cold or flu is to wash your hands frequently with soap and water or with an alcohol-based sanitizer. Also, try to notice and stop yourself when you're about to rub your eyes or nose or bite your nails. And — most important — get a seasonal flu vaccine every year and the H1N1 (swine) flu vaccine when it's available. Some people will always be careless about spreading their germs, but you don't have to catch them.
