Communicable Diseases

• Pathogens are microorganisms that cause infectious diseases.
• Pathogens may be viruses, bacteria, protists, or fungi. They may infect plants or animals and can be spread by direct contact, by water or by air.
• Bacteria and viruses may reproduce rapidly inside the body
• Bacteria may produce toxins that damage tissues and make us feel ill
• Viruses live and reproduce inside cells, causing cell damage
• Bacteria are very small living cells
• Bacteria make you feel ill by producing toxins
• Viruses are not cells, they are tiny
• Viruses can reproduce rapidly inside your body
• Viruses live inside your cells and replicate themselves using the cells machinery. The cells will usually then burst, releasing the viruses into your body. The cells bursting is what makes you feel ill.
• Protists are single-celled eukaryotes
• There are lots if different types of protists but they are all eukaryotes and most are single celled
• Some protists are parasites. Parasites live on or inside other organisms and can cause them damage. They're often transferred by a vector
• Fungi come in different shapes
• Some fungi are single celled, while others have a body made if hyphae. These hyphae can grow and penetrate human skin and the surface of plants, causing diseases. The hyphae can produce spores, which can be spread to other plants and animals
• Pathogens can be spread through water:

  • water - some pathogens can be picked up by drinking or bathing in dirty water - e.g. cholera
  • air - pathogens spread via droplets
  • direct contact