Principles of Disease and Epidemiology

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Microbiology
Chapter 14
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1

Pathology

Study of disease

2

Etiology

Study of the cause of disease

3

Pathogenesis

Development of disease

4

Infection

Colonization of the body by pathogens

5

Disease

An abnormal state in which body is not functioning normally

6

Normal flora

Microorganisms that inhabit us but do not cause disease in or on an organism under normal conditions

7

Microbial antagonism

Competition between microbes

8

Three ways normal flora protect the host

  • Occupying niches that pathogens might occupy
  • Producing acids
  • Producing bacteriocins
9

Probiotics

Live microbes applied to or ingested into the body

Intended to exert a beneficial effect

10

Symbiosis

The relationship between normal microbiota and the host

11

Three types of symbiosis

  • Commensalism
  • Mutualism
  • Parasitism
12

Commensalism

One organism benefits, one organism unaffected

13

Mutualism

Both organisms benefit

14

Parasitism

One organism benefits at expense of another

15

Koch's Postulates

  • Certain organisms cause certain diseases
  • Same microorganism must be present in every case of the disease
  • Must isolate the microorganism from the diseased host and grow in pure culture
  • The microorganism must produce the same disease when inoculated into susceptible host
  • The microorganism must be recovered from the inoculated host again in pure culture
16

Symptom

Change in body function that is felt by a patient

17

Sign

Change in a body that can be measured or observed as a result of a disease

18

Syndrome

A specific group of signs and symptoms that accompany a disease

19

Communicable disease

Spread from one host to another

20

Contagious disease

Easily spread from one host to another

21

Noncommunicable disease

Is not transmitted from one host to another

22

Incidence

Fraction of a population that contracts a disease during a specific time

23

Prevalence

Fraction of a population having a specific disease at a given time

24

Sporadic disease

Disease that occurs occasionally in a population

25

Endemic disease

Disease that is constant in a population

26

Epidemic disease

Disease that is acquired by many hosts in a short amount of time

27

Pandemic disease

Worldwide epidemic

28

Acute disease

Symptoms develop rapidly

29

Chronic disease

Disease develops slowly

30

Subacute disease

Symptoms between acute and chronic

31

Latent disease

Disease with period of no symptoms when patient is inactive

32

Herd immunity

Immunity in most of a population

33

Local infection

Pathogens limited to a small area of the body

34

Systemic infection

An infection throughout the body

35

Focal infection

System infection that began as a local infection

36

Bacteremia

Bacteria in the blood

37

Septicemia

Growth of bacteria in the blood

38

Toxemia

Toxins in the blood

39

Viremia

Viruses in the blood

40

Primary infection

Acute infection that causes initial illness

41

Secondary infection

Opportunist infection after a primary infection

42

Subclinical diseases

No noticeable sign or symptom

43

Predisposing factors for infection

  • Climate and weather
  • Chemotherapy
  • Inherited traits
  • Fatigue
  • Age
  • Lifestyle
44

Incubation period

Microorganism is present but host is not showing any sign of disease

45

Prodromal period

Short period of mild symptoms

46

Period of illness

Acute disease process

47

Period of decline

Signs and symptoms subside

48

Period of covalescence

Person regains strength and body returns to the pre-diseased state

49

Reservoirs of infection

Continual sources of infection

50

Ways to transmit a disease

  • Contact
  • Vehicle
  • Vector
51

Transmission of disease through contact

  • Direct: requires close association between infected and susceptible host
  • Indirect: spread by formites
  • Droplet: airborne
52

Transmission of disease through vehicle

  • Transmission via an inanimate object:
  • Food
  • Water
  • Air
53

Transmission of disease through vector

  • Arthropods: fleas, ticks, mosquitos
  • Mechanical: arthropod carries disease on feet
  • Biological: pathogen reproduces in vector
54

Nosocomial infection

  • Acquired as result of hospital stay
  • MO in environment
  • Compromised status of host
  • Chain of transmission in hospital
55

How to control a nosocomial infection

  • Cleanliness
  • Hand washing
  • Disinfection
56

Epidemiology

Study of when and where diseases occur and how they are transmitted

57

Morbidity

Incidence of a specific, notifiable disease

58

Mortality

Deaths from notifiable disease