B5 communicable diseases

B5.1 health and disease

  • diet, genes, stress and life situations have a big effect on physical and mental wellbeing
  • different types of diseases often interact with each other
    • viruses living in cells can trigger cancers
    • defects in the immune system increases the likely hood of having a communicable disease
    • immune reactions can trigger allergies
    • severe physical health issues can lead to poor mental health
    • malnutrition can cause cardiovascular disease, obesity, type 2 diabetes, cancer
  • A communicable disease is caused by pathogens such as virus or bacteria, it can be passed through direct ways or indirect ways

B5.2 pathogens and disease

  • communicable diseases are caused by infectious microorganisms called pathogens (bacteria, fungus, virus, protists)
  • Bacteria and virus reproduce quickly inside your body
    • bacteria produces a toxin that makes you feel ill
    • virus lives inside the cell and reproduces causing cell damage
  • pathogens can be spread indirectly or directly:
    • air; bacteria, virus, and fungal spores can be transmitted from one plant or animal to another. Droplet infection is when a person sneezes or coughs and water droplets containing the pathogens are inhaled by another person
    • direct contact;
    • STD’s are transmitted via sexual contact
    • insects such as mosquitos act like vectors and carry pathogens from one individual to another
    • some pathogens can be transmitted through the skin, through cuts, scratches, or needle punctures.
    • water; drinking water that contains pathogens means they will get into your digestive system. Fungal spores in splashes of water can spread plant disease

B5.3 growing bacteria in the lab (nvm triple only)

B5.4 preventing bacterial growth (triple only again)

B5.5 preventing infections

  • our modern understanding of pathogens comes from:
    • Ignaz Semmelweiss worked as a doctor before bacteria’s and viruses were discovered, he proposed that doctors wash their hands between patients to reduce transition of disease and number of deaths. It took a long time for other doctors to believe him as viruses and bacteria weren’t discovered yet.
    • Louis Pasteur showed that microorganisms cause diseases and developed vaccines against rabies and anthrax
    • Joseph Lister used antiseptics to destroy pathogens in the operating theatre
  • Spread of disease can be stopped by:
    • hygiene, hand washing, disinfectants, keeping raw meat away from cooked
    • isolating infected individuals
    • destroying/controlling vectors. mosquitos and other insects
    • vaccinations, plants can’t be vaccinated because they don’t have an immune system

5.6 Viral diseases

  • Measles:
    • caused by droplet infection
    • causes skin rashes and fever
    • fatal
    • no cure
    • prevented by isolation and vaccines
  • HIV/AID:
    • caused by direct contact, sexual or infected blood/breast milk
    • early stage causes mild flu-like symptoms
    • late stages destroy the immune system so much the body can’t fight cancer or even a simple cough and die
    • fatal if not controlled by antiretroviral drugs
    • no cure, no vaccine
    • prevented by condoms, screening blood, and bottle feeding children from infected mothers
  • Tobacco mosaic virus (TMV)
    • spread by contact and vectors
    • causes discolouration on leaves and destroys cell so plant cannot photosynthesis
    • no treatment
    • prevented by good field hygiene and pest control