- Bacteria, Fungi, Virus
- Semelweiss, washing hands stopped childbed fever
- spreading disease; coughing, cuts, stds
- preventing infection; mucus, acid, cuts(scabs),skin is a physical barrier, immune system
- white blood cells (toxins/ anti toxins)
- Phagocytes, antibodies, anti toxins.
- vaccinations, we cannot kill viruses as they break into our cells and cause them to burst