Communicable diseases

• Health is a state of physical and mental wellbeing
• Ill health can be caused by communicable diseases (flu, ebola, covid) or non-communicable diseases (heart disease, arthritis, cancer)
• Factors that have an effect on mental and physical stress:

  • Diet: Not enough food or type of food can lead to malnutrition, scurvy, rickets. A high diet in fat or sugar can lead to obesity
  • Stress: Too much stress can lead to heart disease or mental health issues
  • Life situation: which part of the world you live in (access to clean drinking water and healthcare), your gender, your financial situation, how many children you have, etc.
• Different diseases and health conditions interact and can make each other worse
• Viruses living in cells can lead to cancer
• HIV attacks white blood cells making it more likely for them to become infected with other pathogens
• Immune reactions can trigger allergies
• Severe physical health can lead to mental illness
• Malnutrition leads to deficiency diseases, obesity or heart disease
• Communicable diseases are caused by pathogens
• Pathogens are microorganisms that cause infectious disease
• Pathogens may be:

  • Bacteria
  • Fungi
  • Viruses
  • Protists
• Pathogens infect both animals and plants
• Bacteria and viruses cause the majority of diseases in people. Once inside your body, they can reproduce rapidly and cause damage.
• Bacteria are single-celled organisms that are much smaller than plant or animal cells and they can have many shapes and sizes. They are important in the environment as decomposers and in your gut
• Bacteria divide rapidly by splitting into two (binary fission)
• Some bacteria can be pathogenic, they secrete toxins which make you ill and cause diseases: food poisoning, cholera, typhoid, whooping cough, gonorrhea, etc.
• Viruses are much smaller than bacteria
• Viruses invade and take over your body cells
• Viruses only reproduce inside host cells and they damage the cell when they do this
• Eventually the virus copies fill the whole host cell and burst it open
• Diseases caused by viruses include: HIV, measles, influenza - flu, colds, mumps, rubella, chicken pox
• Pathogens are spread by air: bacteria, virus and fungal spores (which cause plant diseases) are carried in the air. In humans, droplet infections is common, where tiny droplets full of pathogens are expelled from your breathing system when you cough, sneeze or talk
• Direct contact: Pathogens such as hepatitis or AIDS/HIV enter the body through direct sexual contact, cuts, scratches. In plants, a tiny piece of infected material can infect an entire new crop.
• By water: fungal spores caried in splashes of water often spread plant diseases. In humans, drinking contaminated water or eating raw, undercooked contaminated food can spread diseases such as cholera and salmonellosis. The pathogen enters your body through your digestive system