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Infectious Diseases 1 > Bubonic Plague > Flashcards

Bubonic Plague Flashcards

1
Q

Bubonic Plague

A

a zoonotic disease vectored by fleas

rodents form the reservoir species

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2
Q

describe the BP

A

the greatest pandemic know to man 1300s

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3
Q

we had steady dramatic exponential growth, how did BP affect this

A

killed 75 million people = significant population

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4
Q

zoonosis

A

a disease which primarily occurs in animals but may

be transmitted to people (BP and LD)

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5
Q

specialized disease on human what would happen

A

ancient - lived in small isolated groups = most would get the disease and become immune or die
small groups can’t support this

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6
Q

how could diseases persist

A

chronic disease - long-lasting
or
zoonosis - supported in animal populations and occasionally affected people

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7
Q

reservoir

A

. the long-term host of the pathogen of an infectious disease
. may not get the disease carried by the pathogen
. may be asymptomatic and non-lethal

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8
Q

describe rabies

A

a zoonosis - reservoir species depend on part of the world
Africa = dogs
Northern America = skunks or raccoons
transmitted by the bite of infectious animal

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9
Q

vector

A

a living organism that transmits the infectious agent between organisms of a different species (biting arthropods (insects/ticks))

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10
Q

how can we get rid of vectors

A
  1. kill the vector
  2. remove the vector’s habitat (mosquito control - drain where they lay eggs)
  3. prevent vector biting
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11
Q

what is the vector and what is the reservoir

A 
vector = flea
reservoir = rodents/rats
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12
Q

why are humans, dead-end host

A

the density of bacteria in blood = not high enough to infect flea

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13
Q

what happens when flea feed on an infected rodent

A

bacteria inside flea stomach MULTIPLY until huge = cannot digest food/further feed = agitated, mobile, bite more > blocked stomach = feed on blood and release back out = infect new host
evolutionary adaptation for fleas to move/bite more

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14
Q

how can you get a human epidemic of BP

A

need lots of infected fleas = need to feed on infected rodents (rats died - fewer hosts for fleas = bite humans

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15
Q

what is the name of the bacteria that causes BP who, when and how was it discovered

A

1894 - Alexandre Yersin - human epidemic of BP proceeded by epidemic in rats = yersinia pestis
(after germ theory established)

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16
Q

what happens when you get BP

A

bacteria get into the lymphatic system - produces and transports lymph fluid = maintain fluid balance + vital part of the immune system
taken up by white blood cells (not killed) travels to lymph nodes = bacteria multiply > large swellings

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17
Q

buboe

A

infected lymph nodes associated with BP

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18
Q

can you treat BP

A

serious but not deadly - untreated = 50% mortality rate

treated = lower by treatment of antibiotics

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19
Q

how do you get septicemic plague

A

lymphatic system drains into bloodstream
untreated - fatal and serious 100% mortality
can be treated with antibiotics but people die quickly 40%

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20
Q

pneumonic plague

A

directly transmitted from person to person - bacteria get into lungs, fatal, kills quickly 100% mortality but very rare

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21
Q

how do we control BP

A

reduce contact between human and rats

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22
Q

Plague of Justinian

A

First Pandemic - killed 25 million people

23
Q

was the population decrease due to the BP in Europe and China

A

75million - 50million 1/3 of population

population halved 123million - 65 million

24
Q

how did uncleanliness spread

A

nobody was bathing - the church was influential - nakedness was a sin / not changing clothes

25
Q

consequences of the Black Death

A
  1. Freedom for the serfs (farming labour intensive - offering wages/freedom)
  2. Bad news for the church (shortage of clergy + lost faith in church - claimed to have answers // beat themselves to repent - cost money = less money for church)
  3. Xenophobia + Anti- Semitism (jews were cleaner/used different wells, less affected)
  4. Pessimism and Hedonism (loss of morale - as people did not know when they would die)
  5. Climate change (after BD - cooler weather - unable to grow crops: populations were slowly growing - after BD - few people to bring in harvest = abandoned farmland => increase in biomass = decrease in CO2 and temp
26
Q

why did we think black death was not caused by bubonic plague

A
  1. bd was not always associated with rats/fleas
  2. bd had a very high virulence
  3. bd may have been directly transmitted
27
Q

Black Death 1347-51

A

most deadly pandemics in human history - though to be caused by BP

28
Q

BD was caused by Yersinia Pestis = no BP today

A

strain no longer exists - modern strains have developed from it - doesn’t explain the virulence

29
Q

Susceptible

A

individuals uninfected by disease and capable of being infected

30
Q

Infected

A

individuals who are infected by the disease and are capable of infecting other individuals in the susceptible category

31
Q

Recovered/Removed

A

individuals who were infected by the disease but are no longer infectious by the virtue of their recovery and immunity or death

32
Q

SIR model

A

a simple model of disease dynamics that tracks the population as it enters and leaves 3 categories (can change boxes over time)

33
Q

how do we eradicate a disease

A

vaccinate a certain fraction of the population

34
Q

what is SIR equation

A

N(total population size) = S + I + R

35
Q

how can you go from susceptible to recovered

A

vaccination

36
Q

how can you go from recovered to susceptible

A

the disease can mutate/immunity

37
Q

Beta b

-BSI

A

the infection rate in the SIR model

individual rate x susceptible x infected (rate out)

38
Q

Gamma y

yI

A

the removal rate in the SIR model

1/ how long disease lasts x infected

39
Q

assumptions of the SIR model

A
  1. population size if infected (people born/migrate)
  2. no age (young/old more susceptible)
  3. incubation period of disease is instantaneous
  4. random mixing between susceptibles and infecteds
  5. immunity if lifelong
  6. disease transmission is direct with no vectors
40
Q

complexities we could add to the SIR model

A
  1. vectored disease
  2. multiple hosts
  3. loss of immunity
  4. carriers who are infectious but asymptomatic
  5. symptomatic but uninfectious category
  6. more realistic mixing
41
Q

Eeyam Plague what did the priest do

A

isolated village and recorded dates of people dying (due to BP
no of S decreases = no of I increases

42
Q

what determines an epidemic

A

increase in the number of infected individuals
BSI > yI (flowin > flow out)
BS > y
BS/y > 1 = FOR AN EPIDEMIC - R0

43
Q

R0

A

average no. of new infections from 1 infected individual in a population of fully susceptible hosts

44
Q

R0 = 1

A

1:1 ratio - no epidemic, might die out

45
Q

R0 < 1

A

stutters along and then dies

46
Q

R0 > 1

A

increase in the no. of cases over time

47
Q

R eff

A

effective growth rate of the disease (over the course of the disease no. of S decreases = effective growth rate decreases)

48
Q

if a sufficiently high proportion of the population is immune

A

then R eff will be below 1 and the disease cannot circulate

the remaining susceptibles are protected by Herd Immunity

49
Q

Herd Immunity

A

a type of community protection from disease that occurs when the vaccination of a portion of the population = provides protection to unvaccinated individuals by making it less likely that any infected individual will contact a susceptible and thus pass on the disease

50
Q

if we vaccinate proportion P then

A

1-P = susceptible fraction

51
Q

disease has high R0

A

vaccinate larger population

52
Q

P > 1 - ( 1 / R0)

A

global herd immunity => eradicate small pox

53
Q

pulse vaccination

A

repeatedly vaccinating a group at risk to control the spread of an epidemic disease

54
Q

ring vaccination

A

concentrating vaccination efforts in the location of known cases to form a buffer of immune individuals

Infectious Diseases 1 (4 decks)

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