Disease causing microorganisms are called pathogens
A pathogen is an organism that causes disease. Your body is naturally full of microbes. Still, these microbes only beget a problem if your vulnerable system is weakened or if they manage to enter a typically sterile part of your body. Pathogens are different and can cause serious illnesses upon entering the body.
There are different types of pathogens: Viruses, Bacteria, Fungi, Parasites…
To protect yourself against them, you must be vaccinated and have your vaccines up to date.