Title: Infectious Disease
1Infectious Disease
2Infectious Disease
- Globally, Infectious disease is still the single
most common cause of death - in 1993, gt16 million people died from infectious
diseases - Many diseases, previously considered conquered,
have once again re-emerged - Tuberculosis
- pneumonia
- food-borne illnesses
3Reemerging Infectious Disease
4Reemerging 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
5What 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
6Reemerging
- 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)
7Reemerging
- Rubeola (measles)(virus)
- Schistosomiasis (helminth)
- Rabies (virus)
- Tuberculosis (bacterium) stricken)
- Yellow fever (virus)
8What causes infectious diseases?
- Microorganisms
- Bacteria
- Virus
- Prion
- Fungus
- Protozoa
- Helminth
- Products from microorganisms
- toxins
9Just 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
10Some 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
11Modes of Transmission
12Why 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)
13Why do people get sick?, contd.
- Host Factors
- age
- gender
- ethnicity
- immune status
- nutritional status
- behavior
- Balance is Key!
14Are 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
15Prevention 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
- dont use antibiotics for viral infections
16Antibiotics
- 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
17Your Immune System
- Part of the lymphatic system
- Primary lymphoid organs
- bone marrow
- spleen
- lymph nodes
- thymus
- Secondary lymphoid organs
- Peyers patches
- tonsils
- appendix
- mucosal associated lymphoid tissues (MALT)
18Immunity
19Cells of the Immune System
- Leukocytes (white blood cells)
- neutrophils (PMNs)
- monocyte/macrophage
- eosinophil
- basophil
- Specialized cells
- B-cells antibodies
- T-cells
20Innate 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
21Innate 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
22Innate immunity
- Second-line defenses, contd.
- Inflammation - normal host response to a
traumatic or infectious injury - heat
- pain
- redness
- swelling
- loss of function
23Innate immunity
- Second-line defenses, contd.
- Phagocytic defenses (by order of appearance)
- PMNs -polymorphonuclear leukocytes (neutrophils)
- monocytes (in blood)
- macrophages (in tissue)
24Adaptive Immunity
- Cell-mediated
- T-cells(CD4, CD8)
- Humoral
- B-cells
- antibodies (immunoglobulins IgM, IgG, IgA, IgE,
IgD) - Both
- complement cascade
25Autoimmune 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
26Prevention
27Epidemiology
28Initial case investigation- looking at reported
cases of interest
- There are three questions to consider
- Who?
- Where?
- When?
29Who?
- Gender
- Age
- Occupation
- Cultural background
- Signs and symptoms
30Where?
- Physical location
- Open or enclosed
- High or low
31 When?
- Time of day
- Time of Week
- Time of month and year
- Duration of event
- Sequence of events
32Epidemiological Guidelines
- 1. Investigate reported cases
332. Form a Hypothesis
343. Come up with a working case definition
354. Design a questionnaire
365. Apply questionnaire to cases and controls
376. Refine case definition, refine hypothesis
- Identify similarities
- Assemble identified case reports
- Exclude disqualified reports
- Test hypothesis against identified cases
38Take Action
398. Communicate Findings