system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Does the phrase "Some viruses target specific cells in the body." mean that when viruses infect the body they completely ignore all other groups of cells or do they infect them equally and only flourish in those cells that favour their growth?
gpt
The outside of cells and virus cells are covered in chemicals. Different cells are covered in different chemicals.

Specific chemicals stick to other specific chemicals. Other chemicals don't do anything. It can help to think of it like many different colors of velcro. Blue velcro only sticks to blue velcro, it doesn't stick to red or green velcro.

If a virus as the correct chemical to stick to a cell, it sticks to that cell and infects it. If a virus does not have the correct chemical, it just bounces off of it and doesn't do anything.

Medicine that targets a specific part of the body works the same exact way. It goes everywhere, but only attaches and does stuff to cells with the right chemical on the outside.