There are lots of different types of germs but they’re all living organisms. We use germs to refer to different types of bacteria, protozoa, fungi and viruses. Bacteria and protozoa are made up of single cells while fungi are multicellular. Viruses can’t survive on their own and have to hijack the machinery of host cells to be able to reproduce. Each of these different types of germs can make us unwell and cause different types of diseases.