Pathogens
Communicable diseases are caused by pathogens: bacteria, viruses, fungi and protists. They can be spread by air, water, contact, vectors or body fluids. Reducing spread means hygiene, vaccination, destroying vectors and isolating infected people.
- Bacteria: salmonella, gonorrhoea. They produce toxins.
- Viruses: measles, HIV, TMV. They reproduce inside cells.
- Fungi: rose black spot.
- Protists: malaria, spread by mosquitoes.
Human defence
The skin, mucus, cilia and stomach acid are non-specific barriers. White blood cells phagocytose pathogens, produce antibodies and produce antitoxins. Vaccination gives a small amount of dead or inactive pathogen so memory cells form and a later response is faster.
Drugs
Antibiotics kill bacteria or slow their growth; they do not work on viruses. Painkillers treat symptoms only. New drugs are tested in the laboratory, then on healthy volunteers, then on patients. Double-blind trials reduce bias.
Taught with support from Joseph Danso, Science Lecturer in London. Book a session.