Infectious diseases
- Pathogens are microorganisms that cause disease. They include bacteria, protozoa, fungi and all viruses.
- Pathogens are spread in different ways:
- Water: Water may contain bacteria such as those that cause cholera.
- Food: Food may contain food –poisoning bacteria such as Salmonella which is found in food that is kept too long or not cooked properly.
- Airborne: Airborne pathogens are carried in the air in droplets and other people can breathe them in.
- Contact: Pathogens can be picked up from touching contaminated surfaces including the skin e.g. Athlete’s foot fungus is transferred from moist surfaces.
- Body fluids: Pathogens can be spread through body fluids such as blood and semen during sex.
- Animal vectors: These are animals that spread disease. Examples are the mosquito which carries the protozoan that causes malaria. It bites other organisms to spread it. House flies can carry the bacterium that causes dysentery. It spreads the disease by carrying the bacterium onto food.