6.5 - 6.6

• Endemic


  Disease occurs routinely in a geographical area
• Epidemic


  Temporary rapid increase in incidence of disease in a geographical area
• Influenza virus transmission


  1. Droplet infection

  2. Direct contact with mucus containing virus

  3. Zoonotic infection: contact with animal waste

  4. Contact with fomites (infected surfaces)
• Influenza virus mode of infection

  1. Injects viral RNA into ciliated epithelial cells

  2. Viral RNA hijacks cell biochemistry to produce new virions

  3. Cell lysis releases virions
• Influenza virus


  • Headache, coughing & sneezing, sore throat, vomiting, fever, muscular / joint pain
  • Symptoms last roughly 5-7 days
• Influenza treatment


  1. Antiviral medication

  2. Antibiotics treat secondary bacterial infection

  3. Management of symptoms e.g. painkillers
• Stem rust fungus transmission

  1. Windborne spores

  2. Host crops (cereal crops & Berberis) leave infected fragments in soil
• Stem rust fungus mode of infection

  1. Presence of water enables spore to germinate & produce hyphae which enter through stomata

  2. Enzymes e.g. cellulase digest plant cells so fungus can absorb nutrients as it grows into mycelium & surrounds tissues
• Stem rust fungus


  • Depletes nutrients
  • Weakens stem
  • Plant loses control of transpiration rate (reduces photosynthesis)
  • Pustules on epidermis release more spores when they burst
• Binomial name of the stem rust fungus on wheat crops is Puccinia graminis
• Malarial parasite


  Plasmodium spp. (a type of single-celled Protozoan)
• Plasmodium spp. mode of transmission and infection

  1. Female Anopheles mosquito acts as vector when it transfers saliva to another organism during feeding

  2. Parasite reproduces asexually in red blood cells in liver, causing lysis
• Plasmodium spp.


  • Paroxysm, liver damage, anaemia caused by damage to red blood cells, shaking, headaches, sweating, muscle pain
• Endemic malaria control


  1. Preventing mosquito bites: mosquito nets, insect repellent

  2. Controlling mosquito numbers: pesticide, chemical treatment of standing water & sewage, introduction of predators for mosquitoes

  3. Drug treatment: combination of quinine, chloroquinine, artemisinin
• Ethical and social implications of controlling endemic malaria

  • Treatments must be evidence based to reduce safety concerns
  • Difficulty obtaining informed consent if knowledge of medical trials is poor
  • Using insecticide kills other organisms
• Social and economic implications of controlling endemic malaria

  • Expensive to implement, especially since many affected countries have low GDP
  • Opportunity cost: money could be spent on other initiatives e.g. malnutrition
  • Preventative measures require change of customs
• Practical difficulties of controlling endemic malaria

  • Widespread endemic
  • 2 hosts involved
  • High antigen variability
  • Parasite enters host cells, which shields it from immune response
• Role of the scientific community in controlling malaria

  • Develop and test evidence-based treatments
  • Develop accurate diagnostic tools to avoid overuse of expensive drugs