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Microbiology > 5.59 > Flashcards

5.59 Flashcards

1
Q

Epidemiology

A

• science that evaluates occurrence, determinants,
distribution, and control of health and disease in a defined
human population

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2
Q

• sporadic disease (example: histoplasmosis, gas gangrene)

A

– occurs occasionally and at irregular intervals

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3
Q

• endemic disease (example: gonorrhea, Dengue fever)

A

– maintains a relatively steady low-level frequency at a moderately regular interval

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4
Q

• holoendemic diseases (example: malaria)

A

– occurs at a high, constant level throughout a population

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5
Q

• epidemic (example: influenza, meningococcal infections)

2

A

– sudden increase in frequency above expected number

– index case – first case in an epidemic

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6
Q

• outbreak

A

– sudden, unexpected occurrence of disease

– usually focal or in a limited segment of population

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7
Q

• pandemic

A

– increase in disease occurrence within large population over wide region
(usually worldwide)

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8
Q

Morbidity rate

A
  • an incidence rate
  • number of new cases in a specific time period per unit of population
equation
# new cases during a specific time over
# individuals in population
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9
Q

Prevalence rate

2

A
  • total number of individuals infected at any one time per unit of population
  • depends both on incidence rate and duration of illness
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10
Q

Mortality rate

A

• number of deaths from a disease per number of cases of the disease

equation
# deaths due to given disease over
size of total population with disease

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11
Q

R0 or R(0), “R-naught” =

A

number of secondary cases one case would

produce in a completely susceptible population

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12
Q

R(0) calculated as a function of 3 primary parameters

A

• duration of contagiousness after a person becomes infected
• likelihood of infection per contact between a susceptible person
and an infectious person or vector
• contact rate

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13
Q

Recognition of an Infectious
Disease in a Population
(2)

A

• involves use of surveillance methods
• cases of a disease recognized by its characteristic
disease syndrome

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14
Q

cases of a disease recognized by its characteristic
disease syndrome
(3)

A

– set of signs and symptoms characteristic of a disease
– signs
– symptoms

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15
Q

– signs

A

• objective changes in body that can be directly observed

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16
Q

– symptoms

A

• subjective changes experienced by patient

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17
Q

• incubation period

A

– period after pathogen entry but before

signs and symptoms appear

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18
Q

• prodromal stage

2

A

– onset of signs and symptoms

– not clear enough for diagnosis

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19
Q

• period of illness

A

– disease is most severe and has

characteristic signs and symptoms

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20
Q

• convalescence

A

– signs and symptoms begin to disappear

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21
Q

skipped
Correlation with a Single Causative Agent
(2)

A

• after recognition of infectious disease in a population, outbreak
correlated with specific pathogen [e.g. HIV/AIDS (early 1980s), SARS
CoV (2003), SARS-CoV-2 (2019-2020)]
• clinical microbiologists help in isolation and identification of pathogen

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22
Q

Recognition of an Epidemic

• 2 types of epidemics

A

common source epidemic

propagated epidemic

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23
Q

threshold density =

A

the minimum number of individuals necessary to continue propagating the disease

24
Q

Herd immunity

A

• resistance of a population to infection and to spread of an
infectious organism because of the immunity of a large
percentage of the population

25
Herd immunity | • level can be altered by
introduction of new susceptible | individuals into population
26
Herd immunity | • level can be altered by changes in
pathogen
27
– antigenic shift –
major change in antigenic character of pathogen
28
– antigenic drift –
smaller antigenic changes
29
1. What Pathogen Caused the Disease? | 3
``` • Kochs postulates (or modifications) are used if possible • clinical microbiology lab • communicable disease ```
30
clinical microbiology lab
– plays important role in isolation and identification of pathogen
31
communicable disease
– can be transmitted from one | host to another
32
source
– location from which pathogen | is transmitted to host
33
• period of infectivity
– time during which source is infectious or is disseminating the organism
34
• reservoir (2)
``` – site or natural environmental location in which pathogen is normally found – sometimes functions as source of pathogen ```
35
Human sources/reservoirs • carrier (3)
– infected host – can be casual (acute or transient) carrier – short time – can be chronic carrier – long time
36
active carrier
– has overt clinical case of disease
37
• convalescent carrier
– has recovered from disease but continues to harbor large | numbers of pathogen
38
• healthy carrier
– harbors pathogen but is not ill
39
• incubatory carrier
– harbors pathogen but is not yet ill
40
Animal reservoirs | 3
* numerous diseases are zoonoses * transmission to human can be direct or indirect * vectors– organisms that spread disease from one host to another
41
1. Airborne Transmission | 3
* pathogen suspended in air and travels ³ 1 meter * droplet nuclei * dust particles also important route of airborne transmission
42
• droplet nuclei | 4
– small particles (1-4 micrometers in diameter) – can remain airborne for long time (hours to days) – can travel long distances – usually propelled from respiratory tract of source organisms by sneezing, coughing, or vocalization
43
Contact Transmission | 3
* coming together or touching of source/reservoir and host * direct contact (person-to-person) * droplet spread
44
• direct contact (person-to-person) | 2
physical interaction between source/reservoir and host | – e.g., kissing, touching, and sexual contact
45
droplet spread
– large particles (>5 micrometers) that travel < 1 meter
46
Vehicle Transmission | • Vehicles =
inanimate materials or objects involved in pathogen transmission – water and food (spread pathogen to multiple hosts) – fomites = inanimate objects: surgical instruments, bedding and eating utensils
47
. Vector-Borne Transmission • external (mechanical) transmission (2)
– passive carriage of pathogen on body of vector | – no growth of pathogen during transmission
48
. Vector-Borne Transmission • internal transmission (3)
– carried within vector – harborage transmission – pathogen does not undergo changes within vector (bubonic plaque: Yersinia pestis in flea) – biologic transmission – pathogen undergoes changes within vector (malaria: Plasmodium spp. in Anopheles spp. mosquito)
49
Why Was the Host Susceptible to the Pathogen? | • two main factors
– defense mechanisms of host | – pathogenicity of pathogen
50
5. How Did the Pathogen Leave the Host? (2)
* active escape | * passive escape
51
active escape
– movement of pathogen to portal of exit [helminths (worms) that migrate through the body of the host]
52
passive escape
– excretion in feces, urine, droplets, saliva, or | desquamated cells [microbes]
53
Control of Epidemics (3)
1. Reduce or eliminate source or reservoir 2. Break connection between source and susceptible individuals\ 3. Reduce number of susceptible individuals
54
1. Reduce or eliminate source or reservoir | 4
– quarantine and isolation of cases and carriers – destruction of animal reservoir – treatment of sewage – therapy that reduces or eliminates infectivity of cases
55
2. Break connection between source and susceptible individuals (4)
– chlorination of water supplies – pasteurization of milk – supervision & inspection of food & food handlers – destruction of insect vectors with pesticides
56
3. Reduce number of susceptible individuals | 2
augment herd immunity: – passive immunity following exposure – active immunity for protection

Microbiology (42 decks)

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