Parirenyatwa entrance. Image credit

Parirenyatwa entrance. Image credit

ZIMSEC O Level Combined Science Notes: Introduction to diseases

  • A disease is an illness
  • Diseases are caused by pathogens
  • Pathogens come in the form of:
  • bacteria, viruses, fungi, protozoa(single celled animals) and small worms
  • Bacteria can be viewed using a light microscope
  • Viruses can only be viewed using special microscopes
  • Pathogens feed on other living organisms
  • hosts- living organisms on which pathogens live
  • contagious diseases- are diseases that can be spread via contact
  • infections diseases-those diseases that can be spread by droplet infection
  • vectors-organisms that carry pathogens from host to host

How pathogens are transmitted

  • By vectors e.g. malaria,sleeping sickness and cholera
  • By physical contact e.g. gonorrhoea,leprosy, tetanus, STDs,ringworms etc
  • By droplets of water or in the air e.g. tuberculosis TB, influenza (Flu), colds
  • By contaminated food e.g. typhoid, malaria, cholera,hepatitis etc

To access more topics go to the Combined Science Notes page