Infection and Response

• Communicable diseases


  Diseases that can be spread from person to person
• Communicable diseases


  Spread by pathogens such as bacteria or viruses
• Non-communicable diseases


  Diseases that cannot be passed from person to person
• 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
• Defective immune system


  Increases the risk of contracting infectious diseases
• Human papilloma virus (HPV)


  Can cause cervical cancer
• Around 3,000 women are diagnosed with cervical cancer every year in the UK, most caused by HPV
• Infection with a pathogen


  Can trigger allergies such as certain cases of asthma or dermatitis
• Physical illness (arthritis)


  Can trigger mental illness (depression)
• 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
  • Damaged immune system can't fight infections and cancer
  • Late stage is AIDS, often fatal
  • Can be treated with antiretroviral drugs that stop virus multiplying
  • Transmitted through exchange of bodily fluids, including unprotected sex and shared needles
• Most children are vaccinated against measles when young
• Antiretroviral drugs for HIV are not a cure, patients must take them for life
• 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 food poisoning


  1. Bacteria secrete harmful chemicals called toxins

  2. Toxins cause symptoms including fever, abdominal cramps, vomiting, and diarrhea
• In the UK, all chickens are vaccinated against Salmonella to control the spread of the disease
• Gonorrhea


  A sexually transmitted bacterial disease
• Antibiotic resistant strains of gonorrhea bacteria are now common
• Stopping the spread of gonorrhea

  1. Using a condom during sexual intercourse

  2. Getting tested and treated with antibiotics if having unprotected sex
• 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 mosquito

  2. Malaria pathogen passes into mosquito

  3. Mosquito bites different person and passes 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 vector (mosquito) from breeding by draining still water and spraying with insecticide

  2. Prevent mosquitoes from biting humans by using mosquito nets treated 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 body
• Parts of the nonspecific defense system

  • Skin
  • Nose and mucus
  • Cilia in trachea and bronchi
  • Stomach acid
• Skin


  • Forms a protective layer covering the body
  • Outer layer of dead cells difficult for pathogens to penetrate
  • Produces sebum which can kill bacteria
  • Can scab over when damaged to prevent pathogen entry
• Nose and mucus


  • Contract pathogens before they enter the breathing system
• Cilia in trachea and bronchi

  • Covered in mucus which contract pathogens upwards towards the throat to be swallowed
• Stomach acid


  • Kills pathogens before they can make their way further down the digestive system
• Even with the nonspecific defense systems, pathogens can still get into the human body and cause serious disease
• The immune system is the body's second line of defense against pathogens
• Immune system


  Protects us against pathogens