Final answer:
The most important action to stop the spread of infection is hand washing. Hand washing is the single most effective behavior to prevent the spread of contagious illnesses.
Step-by-step explanation:
The most important action to stop the spread of infection is hand washing. Hand washing is the single most effective behavior to prevent the spread of contagious illnesses. This is because microbes, which are tiny organisms that can only be seen with microscopes, are ubiquitous and can live on surfaces like doorknobs, money, and our hands. If we touch these surfaces and then touch our face, the microbes can enter our body and make us sick.