Final answer:
To avoid risk of a computer virus infection, do not establish any digital connection with the infected computer. This includes not sharing media, not connecting to the same network, and not opening any emails or documents from the infected machine.
Step-by-step explanation:
When interacting with a computer that is infected with a virus, the only way to have no risk of your own computer becoming infected is to not establish any kind of digital connection. Unlike the physical world where a microbiologist would suggest washing hands to prevent the spread of microbes, in the digital world, the equivalent would be to avoid sharing any media, not to connect to the same network, and to refrain from opening any emails or documents from the infected machine. A virus cannot infect your computer if there is no form of connection, just as microbes cannot make you sick if they do not make contact with you.