DISEASE E&E (Disease Emergence 1)

Question 1

ProMED:

Answer 1

-international society for infectious diseases
-staff around the world collect reports of disease and outbreaks
-have a one health approach

Question 2

> 70% of newly emerging infections:

Answer 2

-derived from animals and wildlife
-proportionally large numbers are RNA viruses (ex. coronavirus, WNV, Ebola)
-humans are susceptible to 1400 infections (61% were derived from animals and wildlife)

Question 3

Bats and viruses:

Answer 3

-almost 1400 different species of bats with different susceptibilities
-intermediate hosts are often involved in leap from bats to humans, but not needed
-exceptional in ability to act as natural reservoir of viruses
>immune system allows low level of infectivity

Question 4

SARS (Severe Acute Respiratory Syndrome):

Answer 4

-spread across 30 countries and regions
-2 ways in Toronto 2003

Question 5

Nosocomial:

Answer 5

-transmitted within hospital

Question 6

MERS CoV (Middle East Respiratory Syndrome):

Answer 6

-first reported in 2012
-all cases linked to travel through the Arabian peninsula
-largest outbreak outside this area occurred in Republic of Korea

Question 7

SARS-CoV-2:

Answer 7

-started from wild animal markets in Asia
-palm civet cat?
-pangolin?

Question 8

Transmission of pathogens within markets:

Answer 8

-contribute to viral emergence
-just have live butchering happen
-mixture of wild and domestic animals

Question 9

Zoonosis:

Answer 9

-any disease or infection that is naturally transmissible from vertebrate animals to humans
-bacterial, viral, parasitic or involve unconventional agents
-major health problem
-many prevent the efficient production of food or animal origin
-create obstacles to international trade in animal products

Question 10

Emerging infectious diseases:

Answer 10

-diseases that have newly appeared in a population or that have existed and are rapidly increasing in incidence (Re-emerging)
-many of these pathogens are not ‘new’, they’ve just emerged in a new host or found a new ecological niche

Question 11

Human immunodeficiency virus (HIV):

Answer 11

-lentivirus
-over 1 million deaths/year
-spilled over from chimpanzees to humans
-multiple cross species ‘spillover’ events
-has become well established and persistent in the human population

Question 12

Spillover:

Answer 12

-a single event where a pathogen from 1 species (reservoir host) moves into another species
>such a movement may result in an outbreak
-may occur with us knowing or not become well established in new host OR
>can result in multiplication and establishment in new out and successfully be transmitted resulting in outbreak
*complex interactions between multiple species in dynamic environments

Question 13

Pathogen spillover:

Answer 13

-occurs when epidemics in host population are not driven by transmission within that population, but transmission from a reservoir populations

Question 14

5 steps for spillover to occur:

Answer 14

1. A source (or reservoir) host of the pathogen must exist
2. Host needs to be infected
3. Pathogen must be released from the source host into an environment that allows its transmission to a spillover
4. Spillover host must be exposed to sufficient quantity of viable pathogen to allow for an effective exposure
5. Spillover host must be susceptible to the pathogen

Question 15

Basic reproduction number (R0):

Answer 15

-number of secondary cases expected from one primary case in a completely susceptible population
-estimate of potential spread under a specific circumstance

Question 16

Factors R0 depends on:

Answer 16

-transmission route (aerosol, sexual, etc.)
-density
-climate
-ventilation
-infectiousness

Question 17

R0=0

Answer 17

-no further transmission
Ex. Lyme’s disease, rabies (in people)

Question 18

R0=1

Answer 18

1. Reservoir
2. Spillover
3. Stuttering chain

Question 19

R0>1

Answer 19

-can result in an epidemic outbreak
-sustainability of outbreak depends on supply of susceptible hosts
Ex. Ebola virus spills over, spreads rapidly but then burns out and disappears
>too virulent to sustain an epidemic over the long term

Question 20

R0>1 steps:

Answer 20

1. Reservoir
2. Spillover
3. Stuttering chain
4. Sustained transmission
5. Epidemics OR spillover

Question 21

R or Re:

Answer 21

-effective reproductive number
-population now has some immunity or interventions have been implemented
-population averaged value over a specific epidemic period

Question 22

Rt:

Answer 22

-reproduction number at a given time
*will change over time depending on:
>immunity in population
>behaviour of hosts
>disease control interventions
>changes/mutations in the pathogen, etc.

Question 23

Monkeypox:

Answer 23

-transmitted from infected animals to humans primarily through bushmeat hunting
>rope squirrels

Question 24

Factors contributing to disease emergence:

Answer 24

1. Environmental changes
2. Human demographics/behaviour
3. Internal travel and commerce
4. Technology and industry
5. Microbial adaption and change
6. Breakdown in public health measures

Question 25

Environmental changes:

Answer 25

-habitat destruction may cause animal populations to cluster allowing for spread of new pathogens
-agricultural expansion into various ecosystems
-climate change

Question 26

Nipah virus emergence in Malaysia:

Answer 26

-emerged as respiratory and neurological disease
-spread rapidly through Malaysia and Singapore
-misdiagnosed at first
-people were infected by close contact with pigs
-eventually pig culling helped to stop the outbreak
-40% mortality in humans

Question 27

Nipah virus emergence good example of:

Answer 27

-‘density-dependent’ pathogen requiring a ‘threshold’ density of susceptible individuals to persist within a population
>most farms were small
>emerged on a new large pig farm

Question 28

Nipah virus reservoir:

Answer 28

-flying foxes
>suffered from some loss of habitat due to several factors (fruiting failure in forest due to El Nino, anthropogenic fires)
-index farm had large fruit orchards, and the tress grew over open pig enclosures
-bats fed in trees and dropped pieces of fruit covered in saliva
*pigs amplified and aerosolized the virus!