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Infectious Disease. Infectious Disease. Globally, Infectious disease is still the single most common cause of death in 1993, >16 million people died from infectious diseases Many diseases, previously considered conquered, have once again re-emerged Tuberculosis pneumonia

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infectious disease2
Infectious Disease
  • Globally, Infectious disease is still the single most common cause of death
    • in 1993, >16 million people died from infectious diseases
  • Many diseases, previously considered conquered, have once again re-emerged
    • Tuberculosis
    • pneumonia
    • food-borne illnesses
reemerging infectious disease4
Reemerging Infectious Disease
  • Why?
    • Human Demographics and Behavior
    • Technology and Industry
    • Economic development and Land Use
    • Microbial Adaptation and Change
    • Breakdown of Public Health Measures
    • and Deficiencies in Public Health
    • Infrastructure
what is an infectious disease
Communicable infection - a disease that is transmitted from person to person (NOT necessarily spread by direct contact!)

influenza

HIV

tuberculosis

chicken pox

Noncommunicable infection - a disease that is not directly transmitted from person to person

malaria

botulism

Rabies

What is an Infectious disease?
reemerging
Cryptosporidiosis (protozoan)

Diphtheria (bacterium)

Malaria (protozoan)

Meningitis, necrotizing fasciitis (flesh-eating disease), toxic-shock syndrome, and other diseases Group A Streptococcus (bacterium)

Pertussis (whooping cough) (bacterium)

Reemerging
reemerging7
Reemerging
  • Rubeola (measles)(virus)
  • Schistosomiasis (helminth)
  • Rabies (virus)
  • Tuberculosis (bacterium) stricken)
  • Yellow fever (virus)
what causes infectious diseases
What causes infectious diseases?
  • Microorganisms
    • Bacteria
    • Virus
    • Prion
    • Fungus
    • Protozoa
    • Helminth
  • Products from microorganisms
    • toxins
just how big are these guys anyway
Just how big are these guys anyway?

Bar is 10 microns

  • viruses
    • 0.05 to 0.1 microns
  • bacteria
    • 0.5 to 1.5 microns
  • red blood cell
    • 5 microns
  • lymphocyte (white blood cell)
    • 5 to 8 microns
  • human sperm
    • 60 microns
some definitions
Some Definitions
  • Infectivity- capacity of an agent to enter & replicate within a susceptible host
  • Pathogenicity - capacity of an agent to cause clinical signs (disease) in a host
  • Virulence - refers to the severity of disease
  • Clinical disease - patient has noticeable symptoms of illness
  • Subclinical disease - no apparent symptoms; if infection persists, patient is known as a carrier
why do people get sick
Why do people get sick?
  • Agent Factors
    • new pathogens (HIV, Nile-like virus)
    • changes in pathogens (acquire antibiotic resistant genes)
  • Environmental Factors
    • changes in environmental conditions (el niño)
    • new environments (natural or man-made)
      • (Sweetwater wetlands)
why do people get sick contd
Why do people get sick?, contd.
  • Host Factors
    • age
    • gender
    • ethnicity
    • immune status
    • nutritional status
    • behavior
  • Balance is Key!
are all bacteria bad
Are all bacteria bad?
  • No!
  • Some bacteria perform essential functions in the body such as:
    • skin: prevents more harmful bacteria from colonizing
    • intestines: helps body break down and absorb certain nutrients; prevents more harmful bacteria from causing intestinal infections
    • vagina: prevents yeasts from overgrowing and causing infections
  • Other body areas are colonized and infections only occur in immunocompromised people
    • nasopharynx, oropharynx, esophagus, stomach
prevention and treatment
Prevention and Treatment
  • Sanitation
    • water and waste treatment
    • personal hygiene
  • Vaccination
    • probably the #1 way to prevent communicable diseases
  • Healthy living (avoidance)
    • practice safe sex
    • avoid IV drugs
    • avoid hospital stays (5% of patients acquire a nosocomial infection)
  • Antibiotics and other drugs
    • use wisely and sparingly
    • don’t use antibiotics for viral infections
antibiotics
Antibiotics
  • Penicillin
    • discovered in 1940s
    • natural product of bread mold
    • thought to be the miracle cure for all infections
    • now many organisms are resistant
  • Antibiotic Resistance
    • antibiotics do not work on viral infections
    • inappropriate use and overuse has resulted in many antibiotic resistant organisms (some organisms can transfer resistance between species)
    • research into new antibiotics has fallen behind
    • many multiply resistant organisms exist
your immune system
Your Immune System
  • Part of the lymphatic system
    • Primary lymphoid organs
      • bone marrow
      • spleen
      • lymph nodes
      • thymus
    • Secondary lymphoid organs
      • Peyer’s patches
      • tonsils
      • appendix
      • mucosal associated lymphoid tissues (MALT)
cells of the immune system
Cells of the Immune System
  • Leukocytes (white blood cells)
    • neutrophils (PMN’s)
    • monocyte/macrophage
    • eosinophil
    • basophil
  • Specialized cells
    • B-cells antibodies
    • T-cells
innate immunity
Innate immunity
  • First-line defenses
    • skin
      • low pH, low moisture, normal desquamation, antibacterial substances
    • vaginal epithelium
      • low pH, normal flora,
    • conjunctival epithelium
      • flushing effects of tears, lysozyme, lactoferrin
    • respiratory epithelium
      • secretory IgA (sIgA), lysozyme, lactoferrin, mucociliary escalator
    • gastrointestinal epithelium
      • hydrochloric acid, gastric enzymes,mucus,sIgA, normal flora
    • urinary epithelium
      • flushing effects of urine
innate immunity21
Innate immunity
  • Second-line defenses (occurs after organism breaches epithelial layer)
    • Initial environment
      • tissue fluids: lysozyme, lactoferrin
      • monocyte/macrophage: engulf & destroy
      • NK cells: recognize altered self cells
      • lymphatic fluid: drains tissues to lymph nodes
innate immunity22
Innate immunity
  • Second-line defenses, cont’d.
    • Inflammation - normal host response to a traumatic or infectious injury
      • heat
      • pain
      • redness
      • swelling
      • loss of function
innate immunity23
Innate immunity
  • Second-line defenses, cont’d.
    • Phagocytic defenses (by order of appearance)
      • PMN’s -polymorphonuclear leukocytes (neutrophils)
      • monocytes (in blood)
      • macrophages (in tissue)
adaptive immunity
Adaptive Immunity
  • Cell-mediated
    • T-cells(CD4, CD8)
  • Humoral
    • B-cells
    • antibodies (immunoglobulins: IgM, IgG, IgA, IgE, IgD)
  • Both
    • complement cascade
autoimmune diseases
Autoimmune Diseases
  • Immune system fails to differentiate between self and non-self and generates antibodies against self proteins
    • lupus - immune cells attack DNA
    • arthritis - immune cells attack cartilage and bone
    • multiple sclerosis - immune cells attack central nervous system
initial case investigation looking at reported cases of interest
Initial case investigation- looking at reported cases of interest

There are three questions to consider:

  • Who?
  • Where?
  • When?
slide29
Who?
  • Gender
  • Age
  • Occupation
  • Cultural background
  • Signs and symptoms
where
Where?
  • Physical location
  • Open or enclosed
  • High or low
slide31
When?
  • Time of day
  • Time of Week
  • Time of month and year
  • Duration of event
  • Sequence of events
epidemiological guidelines
Epidemiological Guidelines

1. Investigate reported cases

6 refine case definition refine hypothesis
6. Refine case definition, refine hypothesis
  • Identify similarities
  • Assemble identified case reports
  • Exclude disqualified reports
  • Test hypothesis against identified cases
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