Ch 10

• reproduction of microorganisms in the human body

  infection
• related clinical signs and symptoms associated with an infectious agent or unknown etiolgoy

  disease
• infection but no clinically observable signs; does not have immune response to the body

  subclinical infection
• reproduction of infectious microorganism but there is no interaction with the body that results in detectable immune response 


  colonization
• colonized but not ill; source of infection on short term or on permanent basis


  carrier
• Prescence of microorganisms on the body or objects movement that spreads disease

  contamination
• HAIs 


  nosocomial
• Goal of epidemiology department is to decrease all preventable HAIs
• CDC agency involved in helping hospital infection control personnel investigating epidemics
• CDC has been around since the 1950s
• National Healthcare Safety Network

  provides incidence rates of common infections
• infectious agent or pathogen 


  wide range of small, primitive life forms
• examples of pathogens/ infectious agents

  bacteria, virus, fungi, protozoa, algae, and lesser known Chlamydiae, Rickettsiae, and prions
• pathogenicity 


  ability of an infectious agent to cause clinical disease

  some readily cause disease and others may be present but not cause clinical disease
• reservoir 


  where microorganisms live and reproduce
• source 


  place from which the microorganisms comes
• reservoir and source are not the same

  histoplasmosis

  fungal infection

  chicken is reservoir

  chicken and fecal droppings are deposited in the soil and serve as source
• Hepatitis A is an example of where the reservoir and source are different

  reservoir is person who handles food

  food handled by person is the source
• person whom the infectious agent is passed

  host
• 3 disease phases of host

  1. incubation
  2. clinical disease
  3. convalescence
• incubation 


  interval between exposure and appearance of the first symptom
• clinical disease stage 


  time interval in which the person exhibits clinical signs and symptoms
• convalescence


  stage of recovery from illness
• During which disease phase is a person contagious?

  any or all
• Infectious cycle

  • reservoir host
  • exit portal
  • transmission
  • entrance portal
  • susceptible host
• direct contact transmission route

  when the susceptible host makes contact with the source of infection which can be either an infected or colonized person
• Indirect contact


  single infective episode when an intervening object is contaminated from contact with an infectious agent and then comes into contact with another individual
• Droplet


   rapid spread of infectious agents through the air over short distances usually 3 feet or less
• Common vehicle


  a contaminated inanimate vehicle/fomite for transmission of the infectious agent to multiple people
• Airborne


  entails long distance (6 feet or more) spread of an infectious agent that uses the air to spread
• Vector-borne


   transmitted by vectors such as mosquitoes, ticks, or fleas
• rubella, colds, or influenza is what kind of transmission?

  droplet
• needlestick with an HIV patient is what kind of transmission route?

  indirect contact
• common vehicles include

  food, water, medications, medical equipment, and medical supplies
• mononucleosis is what kind of transmission?

  direct contact
• malaria is what kind of transmission?

  vector-borne
• tuberculosis, chickenpox, shingles, and measles are what kind of transmission ?

  airborne
• How is airborne different from droplet?

  size- airborne is smaller and can travel farther distances than droplet
• How is common vehcile different from direct contact?

  common vehicle infects multiple people, direct contact is a single infection
• nonspecific defense mechanisms 


  skin, cilia, mucus, secretions, acidic environments (urinary and GI), hygiene