A recent report warns that you are at far greater risk of passing on an infection by shaking someone's hand than by sharing a kiss.
The report also notes that regular handwashing may be more effective than drugs in preventing the spread of respiratory viruses such as influenza and SARS.
Germs that cause stomach infections such as salmonella, campylobacter and norovirus can also circulate directly from person to person via your hands. Stomach germs can also be passed on if you put your fingers in your mouth or forget to wash your hands before preparing food.
Breaking the chain of infection depends on how well you wash your hands.