Infection and Response

• Communicable diseases


  Diseases that can be spread from person to person
• Non-communicable diseases


  Diseases that cannot be passed from person to person
• Diseases can be a major cause of ill health
• Health


  The state of physical and mental well-being
• Ill health can be caused by communicable and non-communicable diseases, poor diet, high levels of stress, and other life situations
• People with a defective immune system


  Are much more likely to suffer from infectious diseases
• Infection with HPV


  Can cause cervical cancer
• Infection with a pathogen


  Can trigger an allergy
• Physical illness (arthritis)


  Can trigger a mental illness (depression)
• Pathogen


  Microorganisms that cause infectious disease
• Types of pathogens


  • Bacteria
  • Viruses
  • Protists
  • Fungi
• Bacteria


  • Reproduce very rapidly under ideal conditions
  • Can divide every 20 minutes
  • Release harmful chemicals called toxins that damage tissues and make us feel ill
• Viruses


  • Cannot be produced by themselves
  • Can only reproduce inside a host cell
  • Invade host cell, reproduce inside, then cause the cell to burst open and die
• Ways pathogens are spread

  • Airborne (e.g. influenza)
  • Water (e.g. cholera)
  • Direct contact (e.g. HIV)
• Reducing the spread of pathogens

  1. Practicing basic hygiene (e.g. handwashing)

  2. Providing clean drinking water

  3. Reducing direct contact between individuals (e.g. using condoms)

  4. Isolating highly infectious patients

  5. Vaccination
• Around 300,000 people in the UK get food poisoning from a type of bacteria every year
• Many bacterial diseases can kill us
• Viruses are very damaging to host cells, causing them to burst open and die
• Drinking water in the UK contains chlorine which kills microbes
• Viruses


  Pathogens that cannot be killed by antibiotics
• Viruses are microorganisms that cause infectious disease
• Measles


  • Highly infectious disease
  • First symptom is fever
  • After 3 days, patient develops red skin rash
  • Virus spreads through coughing/sneezing droplets
  • Can cause complications and be fatal
• HIV


  • First symptom is flu-like illness
  • Virus attacks immune system cells
  • Immune system becomes severely damaged
  • Patient can contract other infections and develop cancer
  • Late stage is AIDS, often fatal
  • Can be treated with antiretroviral drugs but not cured
  • Transmitted through exchange of bodily fluids
• Most children are vaccinated against measles when young
• Patients on antiretroviral drugs for HIV do not develop AIDS and can have normal life expectancy
• Communicable disease


  A disease that is passed from person to person by a pathogen
• Pathogen


  A microorganism that causes an infectious disease
• Unlike viruses, bacteria can be killed by antibiotics
• Salmonella food poisoning


  A bacterial disease caused by ingesting infected food
• Salmonella bacteria are sometimes found in poultry such as chicken, but in the UK all chicken are vaccinated against Salmonella
• Gonorrhea


  A sexually transmitted bacterial disease
• In the past, gonorrhea was easily treated using the antibiotic penicillin, but antibiotic resistant strains are now common
• Stopping the spread of gonorrhea

  1. Using a condom during sexual intercourse

  2. People with unprotected sex getting tested and treated with antibiotics
• Malaria


  A very common disease in certain parts of the world that causes over 400,000 deaths every year
• Malaria


  • It is a communicable disease, meaning it is spread by a pathogen
  • The malaria pathogen is an example of a protist
• Life cycle of malaria pathogen

  1. Infected person is bitten by a mosquito

  2. Malaria pathogen passes into the mosquito

  3. Mosquito bites a different person and passes the malaria pathogen to them
• Vector


  The mosquito that carries the malaria pathogen from one person to another
• Preventing the spread of malaria

  1. Stop the mosquito vector from breeding by draining areas of still water

  2. Spray areas of still water with insecticide to kill mosquitoes

  3. Prevent mosquitoes from biting humans by sleeping under a mosquito net, especially one sprayed with insecticide
• It is virtually impossible to kill all mosquitoes
• Nonspecific defense system


  The body's first line of defense against pathogens, preventing them from entering the human body