Infectious Disease - PowerPoint PPT Presentation

• 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

• 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

influenza

HIV

tuberculosis

chicken pox

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

malaria

botulism

Rabies

Diphtheria (bacterium)

Malaria (protozoan)

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

Pertussis (whooping cough) (bacterium)

• Rubeola (measles)(virus)
• Schistosomiasis (helminth)
• Rabies (virus)
• Tuberculosis (bacterium) stricken)
• Yellow fever (virus)

• Microorganisms
• Bacteria
• Virus
• Prion
• Fungus
• Protozoa
• Helminth
• Products from microorganisms
• toxins

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

• 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

• 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)

• Host Factors
• age
• gender
• ethnicity
• immune status
• nutritional status
• behavior
• Balance is Key!

• 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

• 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

• 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

• 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)

• Leukocytes (white blood cells)
• neutrophils (PMN’s)
• monocyte/macrophage
• eosinophil
• basophil
• Specialized cells
• B-cells antibodies
• T-cells

• 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

• 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

• Second-line defenses, cont’d.
• Inflammation - normal host response to a traumatic or infectious injury
• heat
• pain
• redness
• swelling
• loss of function

• Second-line defenses, cont’d.
• Phagocytic defenses (by order of appearance)
• PMN’s -polymorphonuclear leukocytes (neutrophils)
• monocytes (in blood)
• macrophages (in tissue)

• Cell-mediated
• T-cells(CD4, CD8)
• Humoral
• B-cells
• antibodies (immunoglobulins: IgM, IgG, IgA, IgE, IgD)
• Both
• complement cascade

• 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

There are three questions to consider:

• Who?
• Where?
• When?

• Gender
• Age
• Occupation
• Cultural background
• Signs and symptoms

• Physical location
• Open or enclosed
• High or low

• Time of day
• Time of Week
• Time of month and year
• Duration of event
• Sequence of events

1. Investigate reported cases

• Identify similarities
• Assemble identified case reports
• Exclude disqualified reports
• Test hypothesis against identified cases