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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
consequences of the Black Death
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
why did we think black death was not caused by bubonic plague
1. bd was not always associated with rats/fleas 2. bd had a very high virulence 3. bd may have been directly transmitted
27
Black Death 1347-51
most deadly pandemics in human history - though to be caused by BP
28
BD was caused by Yersinia Pestis = no BP today
strain no longer exists - modern strains have developed from it - doesn't explain the virulence
29
Susceptible
individuals uninfected by disease and capable of being infected
30
Infected
individuals who are infected by the disease and are capable of infecting other individuals in the susceptible category
31
Recovered/Removed
individuals who were infected by the disease but are no longer infectious by the virtue of their recovery and immunity or death
32
SIR model
a simple model of disease dynamics that tracks the population as it enters and leaves 3 categories (can change boxes over time)
33
how do we eradicate a disease
vaccinate a certain fraction of the population
34
what is SIR equation
N(total population size) = S + I + R
35
how can you go from susceptible to recovered
vaccination
36
how can you go from recovered to susceptible
the disease can mutate/immunity
37
Beta b | -BSI
the infection rate in the SIR model | individual rate x susceptible x infected (rate out)
38
Gamma y | yI
the removal rate in the SIR model | 1/ how long disease lasts x infected
39
assumptions of the SIR model
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
complexities we could add to the SIR model
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
Eeyam Plague what did the priest do
isolated village and recorded dates of people dying (due to BP no of S decreases = no of I increases
42
what determines an epidemic
increase in the number of infected individuals BSI > yI (flowin > flow out) BS > y BS/y > 1 = FOR AN EPIDEMIC - R0
43
R0
average no. of new infections from 1 infected individual in a population of fully susceptible hosts
44
R0 = 1
1:1 ratio - no epidemic, might die out
45
R0 < 1
stutters along and then dies
46
R0 > 1
increase in the no. of cases over time
47
R eff
effective growth rate of the disease (over the course of the disease no. of S decreases = effective growth rate decreases)
48
if a sufficiently high proportion of the population is immune
then R eff will be below 1 and the disease cannot circulate the remaining susceptibles are protected by Herd Immunity
49
Herd Immunity
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
if we vaccinate proportion P then
1-P = susceptible fraction
51
disease has high R0
vaccinate larger population
52
P > 1 - ( 1 / R0)
global herd immunity => eradicate small pox
53
pulse vaccination
repeatedly vaccinating a group at risk to control the spread of an epidemic disease
54
ring vaccination
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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