I finally know the second part of my main question! Pathogen!! Types of pathogen include bacteria, viruses, parasites, and fungi. These things can trigger your immune system immediately. Here is an explanation of all the pathogens:
Bacteria attack and digest tissue for themselves so they can have something to eat. Bacteria are scavengers, so they want to take as much as they can before the immune response destroys them. Bacterial diseases include strep throat, tetanus, Lyme disease and meningitis. Cavities are also just sugar-loving bacteria that eat away at your teeth. Viruses are a bit different. They invade cells and occupy them, so the virus gets all the nutrients they need to survive. They use the cell to multiply so when the cell dies each virus goes for another cell, multiplying even more. If a virus finds itself outside a warm cushy body, like on a door handle, it dies almost instantly because it doesn’t have any organisms to invade. Viral diseases include the chicken pox, Ebola, and HIV. Over 200 viruses are responsible for what we call the “common cold”. Parasites are also scavengers but are usually a little larger than bacteria. They feed on the tissue of the host organism and lay their eggs inside the bloodstream to reproduce. Protozoa are also Parasites, except they don’t lay eggs. Drinking dirty water is a common way to get a parasite infection. Common parasite infections include Giardia, tapeworm, hookworm and roundworm infections.