Unit 4: Infectious disease

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Unit 4 Infectious disease
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Infectious Disease

• Infectious diseases remain a leading cause of
  death in low-income countries
• Not as big of a concern in developed countries
  such as Canada
• Except in people with poor immune systems
• Infants
• The elderly
• Malnourished people
• Alcohol abusers

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Infectious Disease

• Caused by infection.
• Infection when a microorganism (ex. Bacteria,
  virus) invades the body which is typically
  accompanied by damage to cells
• Invasion is followed by a latent period, which is
  the time between infection and the development of
  symptoms/signs

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Pathogens

• Pathogens are disease causing agents
• Exs
• Viruses non-living organisms composed of DNA or
  RNA enclosed in a protein coat.
• Require host to survive
• Bacteria single-celled organisms that can live
• outside of the body
• Fungi
• Parasites (ex. Tapeworms, amoeba)
• Survive by compromising host

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Antigens

• All pathogens contain antigens
• Antigen antibody-generating
• It is a protein/sugar on a microorganisms
  surface that our immune system recognizes and
  tries to eliminate
• Antigens are how our body knows that a specific
  pathogen has entered our body

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Natural Defence to infection

• Skin
• Cilia
• Mucus
• Elevated body temperature

A pathogen can enter through a lesion (cut) in
the skin
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Natural Defence to infectionThe Immune system

• Immune system complex system in the body that
  helps protect against pathogens and disease
• Key immune components
• Macrophages
• Antibodies
• B-Cells
• T-Cells
• Memory B-Cells
• Memory T-Cells

Organs of the immune system
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Macrophages

• Macrophages (big eaters) a cell that surrounds
  and digests foreign matter

Macrophage ingesting 2 red blood cells
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Antibodies

• Antibodies Specific proteins that stick to the
  specific antigens of pathogens.
• They cause pathogens to clump so
• they cannot enter cells
• they can be more effectively excreted

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Key immune components

• B-cells once activated, have one of 2 fates
• Become plasma cells which secrete antibodies
• Become memory cells to fight off the same
  infection in the future
• T-cells there are several types
• Helper T cells help other immune cells
• Cytotoxic T cells destroy virally infected cells
• Memory T cells fight off the same infection in
  the future
• Regulatory/suppressor T cells make sure response
  isnt overactive

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Key Immune components

• Memory T-cells/ memory B-cells created the first
  time a certain type of pathogen enters the body
  while regular B-cells and T-cells are fighting
  infection.
• The next time the same pathogen enters the body,
  they are already ready, waiting to eliminate that
  pathogen.
• Therefore, the secondary response is much
  quicker!

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Ab mg/ml serum
Days
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Immunity

• Immunity refers to the ability of your body to
  resist infection so that signs/symptoms and
  disease do not develop
• Ex. I already had chicken pox once, so now I am
  immune to it (I wont get it again)

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4 Ways of Getting Immunity

• Natural Immunity (occurs naturally)
• Active Natural get exposed to pathogen
• Passive Natural Fetus receives antibodies from
  mother
• Infant receives antibodies from breast milk
• Conferred Immunity (received from an outside
  source)
• Active Conferred vaccination (ex. A flu shot)
• Passive Conferred get antibodies
• The Active methods are mostly permanent
• The Passive methods are temporary

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Transmission of Infectious Disease

• Many infectious diseases are communicable, which
  means that they can be passed from one person to
  another in one of the following ways
• Direct contact
• Indirect contact
• Airborne transfer
• Contaminated water
• Vector transmission

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Chain of Infection
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Infectious Diseases
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Classifications of Disease Outbreak

• Endemic restricted or peculiar to a locality or
  region
• Malaria is endemic to Africa
• Epidemic affecting or tending to affect an
  atypically large number of individuals within a
  population, community, or region at the same
  time excessively prevalent
• AIDS is epidemic
• Pandemic occurring over a wide geographic area
  and affecting an exceptionally high proportion of
  the population
• H1N1 is likely to be pandemic throughout the
  world this coming flu season
• http//medlineplus.gov/

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Bacterial Infectious Diseases

• Cholera- caused by vibrio cholerae bacterium
• Diarrhoeal infection, can result in death
• Fecal-oral transmission
• 6 significant and fatal outbreaks throughout
  recent history, still endemic in many countries
• Leprosy- caused by mycobacterium leprae bacterium
• Direct, indirect transmission
• 213000 current cases, mainly in Asia, Africa
• Untreated can cause skin, nerve, limb, eye damage
• curable

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Bacterial Infectious Diseases

• Meningococcal meningitis- caused by several
  different types of bacteria
• Results in severe infection of the meninges- thin
  linings that surround the brain and spinal cord
• Can cause severe brain damage and kills 50 of
  untreated cases
• Typically indirect transmission
• Symptoms include stiff neck, high fever, light
  sensitivity, confusions, headaches and vomiting

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Curing bacterial infections

• Bacterial infectious diseases can be cured by
• ____________________________________

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Viral Infectious Diseases

• Common Cold- Typically caused by rhinovirus or
  coronavirus
• Symptoms include sore throat, runny nose and
  fever
• Influenza- caused by various strains of influenza
  virus
• Symptoms include high fever, dry cough, headache,
  sore throat, muscle pain, runny nose
• Both Most common transmission is through
  indirect contact i.e.. Shaking hands then
  touching eyes, nose, mouth
• No cure for either, immune systemdefence

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Do you have the cold or the flu?
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H1N1 (Swine Flu)

• A subtype of the influenza virus which has genes
  from 2 pig, a human and a bird virus
• Symptoms include fever, cough, sore throat, runny
  nose, body aches, chills, fatigue, diarrhea,
  vomiting
• People over 60 may have some immunity to it
• The effects of the recent outbreaks have been
  relatively minor
• BUT! What if the virus mutates further and it
  becomes more aggressive??

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Parasitic Infectious Diseases

• Malaria- caused by plasmodium parasites
• Vector transmission by mosquitoes
• Nearly 1 million deaths in 2008 (mostly African
  children)
• Acute symptoms similar to flu, can lead to
  anaemia, respiratory problems
• Antimalarial drugs exist, but are becoming
  resistant

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Sexually Transmitted Infectious Diseases

• AIDS
• Genital Herpes
• Hepatitis B
• Gonorrhoea
• Chlamydia
• Syphilis
• to be discussed during the STD unit

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Control of Infectious Disease Personal Level

• Hand washing, alcohol based sanitizers
• Cover mouth/nose when you cough/sneeze
• Avoid touching eyes, nose or mouth
• Bug spray
• Drink clean water
• Stay home if sick

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Control of Infectious diseaseCommunity level

• Pasteurization heat-treating fluids (ex. Milk)
• Antibiotics kill microorganisms such as bacteria
• Vaccination ex. Polio, flu vaccine
• Adequate housing minimizes exposure to pathogens
• Nutrition eating well raises your immunity
• Public sanitation

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Control of Infectious Disease at Community Level
Antibiotics

• Antibiotics kill or inhibit the growth of
  bacteria
• Their discovery, specifically the discovery of
  penicillin (Flemming, 1928), has dramatically
  decreased death from infectious disease
• However, natural selection (survival of the
  fittest) has occurred and now many bacteria that
  exist today are resistant to several antibiotics

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Control of Infectious Disease at Community Level
Vaccination

• Live, weakened, inactive or killed forms of the
  pathogen are administered to the patient
• This administration is too low to cause symptoms,
  but sufficient to stimulate the production of
  antibodies
• When later exposed to the pathogen in its natural
  form, your body is already prepared to fight it
  with antibodies, and it is eliminated before
  signs/symptoms can occur

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Successful Cases of Vaccine UsagePolio

• Caused by poliovirus
• Fecal-oral transmission
• Majority of cases show no symptoms, paralysis in
  some
• Vaccine developed by Jonas Salk (1952)
• Mostly eradicated- 1982-350,000 cases,
• 2006 1997 cases
• Still endemic in Nigeria, India, Pakistan and
  Afghanistan

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Successful Cases of Vaccine UsageSmallpox

• Caused by variola virus
• Killed 30 of infected, left others with scars,
  blindness
• Edward Jenner inoculated people with cowpox,
  found it protected from smallpox
• Effective vaccine developed and began worldwide
  administration in 1950s
• 1950s-50 million smallpox cases last case of
  smallpox-1978
• WHO certified it as completely eradicated
• in 1979 only disease ever with such success

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Third world infectious disease control

• Immunization (ex. giving them vaccines)
• Insecticides
• Clean drinking water
• Public Hygiene
• General economic and social development