They use various ways to enter the body and cause infection
They can infect both plants and animals
Bacteria
Very small living cells that can reproduce rapidly inside the body and produce toxins that damage cells
Viruses
Not cells, much smaller than bacteria, live inside host cells and use the cell's machinery to reproduce, causing the cell to burst and release new viruses
Protists
Single-celled eukaryotes, some are parasites that live inside other organisms and are often transferred by vectors
Fungi
Can be single-celled or have a body made up of hyphae that can penetrate human skin and plant surfaces, producing spores that can spread to other plants and humans
Ways pathogens can be spread
Water
Air
Direct contact
How viruses cause cell damage
Viruses live inside host cells and use the cell's machinery to reproduce, causing the cell to burst and release new viruses
