communicable diseases

• communicable disease = caused by pathogens, passed from one organism to another
• pathogen = microorganisms that cause disease
• HPV infection can lead to cervical cancer
• infection with HIV reduced the ability of the immune system to overcome other infections
• colds caused by a virus can lead to allergies
• a pathogen is a disease causing microorganism
• a pathogen is either a bacterium, virus, protist or fungi
• bacterial diseases: salmonella and gonorrhoea
• viral diseases: measles, HIV, HPV
• binary fission = bacteria causes disease by dividing rapidly into 2
• bacteria produces toxins and directly damages your cells
• viruses cause disease by taking over the cells of your body, they live reproduce inside the cells, damaging and destroying them
• common disease symptoms = high temp, headaches and rashes
• pathogens spread through air = droplets are expelled through the air and breathed in by others, spores in wind for plants
• measles and tuberculosis are caused by coughing, sneezing and talking
• direct contact = HIV and AIDs
• direct contact in humans = STIs through contact, sex and scratches
• pathogens spread through water (humans) = eating raw or uncooked food or drinking water (contaminated)
• pathogens spread through water (plants) = fungal spores in water
• diseases in water = salmonella and cholera
• toxins = harmful chemical produced by a microorganism
• what is a pathogen?

  a pathogen is a disease causing microorganism, a pathogen is either a bacterium, virus, protist or fungi.
• bacterial disease examples

  salmonella, gonorrhoea
• viral disease examples

  measles, hpv
• bacteria

  used to make food such as yoghurt

  people have 1-2kg of bacteria in their body

  they produce toxins

  they divide by binary fission

  can be used to make medicines

  single celled
• viruses

  in plants, viruses and fungi are the most common pathogen

  viruses are smaller than bacteria

  they usually have regular shapes

  cause disease in every type of living organism

  take over cells in body

  live and reproduce inside cells
• how do bacteria cause disease?

  by dividing rapidly into two (binary fission) they produce toxins and directly damage your cells.
• how do viruses cause disease?

  viruses take over the cells of the body, they live and reproduce inside the cells, damaging and destroying them.
• pathogens spread through air

  droplets are expelled through the air and breathed in by others

  spores in wind for plants

  caused by coughing, sneezing or talking

  measles and tuberculosis are spread through this
• pathogens spread through direct contact

  in plants, pieces of infected tissue can infect an entire crop

  in humans = STIs through contact, sex and scratches

  HIV + AIDS
• pathogens spread through water

  in humans = eating raw or uncooked food or drinking contaminated water

  in plants = fungal spores in water

  salmonella, cholera
• what is a toxin?

  a harmful chemical produced by a microorganism
• a protist is a single celled eukaryote and are often transferred by a vector which carries the disease without being affected by it
• measles


  • spread by droplets
  • viral
  • red skin rash and fever
  • fatal if complications arise
• HIV/AIDs


  • viral
  • starts with mild flu symptoms
  • when the immune system can no longer deal with infections or cancers, disease becomes AIDs
  • no cure
  • spread via exchange of bodily fluids
• salmonella


  • bacterial
  • fever, abdominal cramps, vomiting
  • found in raw meat and eggs
  • poultry vaccinated to prevent
  • good cooking hygiene to prevent poisoning
• gonorrhoea


  • bacterial
  • sometimes symptomless, thick yellow discharge and longterm pelvic pain
  • treated with antibiotics
  • prevented by condoms
• malaria


  • caused by protists
  • mosquitoes act as a vector - transfers the protist from an infected animal to another animals blood vessels
  • causes fever, can be fatal
  • prevented by insecticides