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Emerging Infectious Diseases (BIOL 325) > Lecture 7: Drivers of Emerging Disease > Flashcards

Lecture 7: Drivers of Emerging Disease Flashcards

1
Q
  1. Up to what percent of emerging diseases are zoonotic in origin?
  2. About what percent of all human pathogens are emerging?
  3. What fraction of new human pathogens are viruses?
A
  1. 75%
  2. 15%
  3. 2/3
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2
Q

What are the 5 stages through zoonotic diseases evolve to become primarily human pathogens?

A
  1. Stage 1: agent only in animals
    - No transmission to humans
  2. Stage 2: primary infection
    - Transmission to humans only from animals
  3. Stage 3: limited outbreak
    - From animals or a few humans
  4. Stage 4: long outbreak
    - From animals or many humans
  5. Stage 5: exclusive human agent
    - Only from humans
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3
Q

True or false: the emergence of a pathogen has multiple drivers.

A

True

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4
Q

What is the most common factor in outbreaks of new diseases with high mortality rates? Why?

A

Ecological changes and agricultural development
- Humans and their animals come closer in proximity to reservoirs of new diseases or their vectors

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5
Q

What drives ecological changes and agricultural development?

A
  • Increase in human population –> increase in demand for livestock or farming
  • Economic opportunity
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6
Q

List the following for Argentine hemorrhagic fever:
1. Causative agent
2. Reservoir
3. Transmission

A
  1. Junin virus
  2. Drylands vesper mouse/corn mouse
  3. Contact with rodent body fluids or excrement
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7
Q

Explain how Argentine hemorrhagic fever spread to humans/how outbreaks occur.

A
  • Grassland was converted to cornfields –> mice made homes in the cornfields
  • Epidemics occur during the corn harvesting season in autumn
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8
Q

List the following for Japanese encephalitis:
1. Causative agent
2. Reservoir
3. Transmission

A
  1. Japanese encephalitis virus
  2. Waterbirds
  3. Bite from Culex mosquitos
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9
Q

Explain how Japanese encephalitis spread to humans/how outbreaks occur.

A
  • Pigs serve as amplifying hosts and are associated with human outbreaks in rural agricultural areas
  • Pig population increases as pork consumption increases
  • Flooded rice fields attract waterbirds and serve as breeding ground for mosquitos
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10
Q

What is bushmeat and how are bushmeat activities linked to outbreaks?

A
  • Meat derived from wild animals for human consumption (important source of protein for many developing countries)
  • Greatest risk occurs when butchering animals
  • HIV, monkeypox, rabis, Ebola outbreaks
  • Lack of knowledge of risks and safety is the major driver
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11
Q

How do animal markets and factory farming contribute to outbreaks?

A
  • Animals are living in cramped and unhygienic conditions
  • Sick animals can easily transmit to nearby animals
  • Different animals in contact with each other increases the risk for spillover events
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12
Q

List some changes in demographics that act as drivers of emerging disease.

A
  • Human population increasing
  • Migration from rural areas to urban areas
  • War or disaster promotes migration
  • People are living longer
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13
Q

List the following for the reemergence of malaria in the Amazon region of Brazil:
1. Causative agent
2. Reservoir
3. Transmission

A
  1. Plasmodium falciparum and P. vivax
  2. Humans
  3. By mosquitos
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14
Q

Explain how the reemergence of malaria in the Amazon region of Brazil occurred.

A
  • Malaria was practically eradicated in the Amazon region by the 1950s
  • 1960s: new highways were built that linked the Amazon region with other parts of the country
  • 1970s: rise in agriculture settlements in the region
  • 1980s: discovery of gold led to mass migration
  • People with malaria brought the disease to the region
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15
Q

What changes in society/behaviors acted as drivers of emerging disease?

A
  • Sexual revolution in 1960s-70s lead to rapid emergence of STIs
  • Antibiotics –> people less scared of getting sick
  • Intravenous drug use
  • Unprotected sex, sex with multiple partners, not regularly testing, not taking preventative medication
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16
Q

Why do childcare settings propagate outbreaks?

A

Because children are in close contact with each other
- High risk of transmitting enteric infections, respiratory infections, and skin infections
- Family members get infected from the child

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17
Q

List the following for Kingella kingae
1. What it is
2. Transmission
3. Diseases it causes

A
  1. Gram-negative coccobacillus that largely colonizes the respiratory tract of children under the age of 4
  2. Person-to-person via respiratory secretions
  3. Bacteremia and skeletal infections
18
Q

How does poor health contribute to emerging disease?

A

Poor health, underlying conditions, AIDS, immunosuppressants and cancer increases the susceptibility to infection

19
Q

What has led to increased HAIs?

A
  • Invasive medical procedures, surgery, indwelling medical devices, prosthetics can introduce pathogens
  • Poor infection control measures can lead to the spread of microorganisms
  • Over usage of antimicrobials lead to resistance bugs
20
Q

1 in _____ hospital patients have a HAI and 1 in _____ nursing home residents have a HAI.

A
  1. 31
  2. 43
21
Q

In 2015, how many HAI cases in acute care were reported? How many of those with a HAI died?

A
  1. 687,000 cases
  2. 72,000
22
Q

How do HAIs spread?

A
23
Q

List the following for fungal meningitis associated with methylprednisolone injections.
1. Causative agent
2. Reservoir
3. Explain how the outbreak happened.

A
  1. Exserohilum rostratum (mainly) and other contaminants
  2. Environment
  3. September 2012: outbreak of fungal meningitis, joint infections, and other infections in the U.S.
    -14,000 methylprednisolone acetate (steroid) vials from the New England Compounding Center were contaminated with various environmental microbes
24
Q

How do non-pathogenic bacteria become pathogenic?

A

Horizontal gene transfer
- Bacteria acquire new pathogenic genetic material

25
Q

What are the mechanisms of horizontal gene transfer. Explain them.

A
  • Transformation: uptake of DNA from external surroundings
  • Conjugation: one cell transfers DNA to another cell via direct contact
  • Transduction: virus introduces foreign DNA to the cell
26
Q

What are pathogenicity islands?

A

Large genomic regions coding for virulence factors that are present on the genomes of pathogenic bacterial strains but absent in nonpathogenic members of the same or related species

27
Q

What are pathogenicity islands generated by?

A

Horizontal gene transfer

28
Q

List the following for cholera:
1. Causative agent
2. Reservoir
3. Trasmission
4. How many serogroups are responsible for outbreaks? Which ones?
5. How do people typically die from cholera?

A
  1. Vibrio cholerae
  2. Marine and estuarine waters; humans
  3. Consumption of contaminated waters by infected human species
  4. 2 of 200 serogroups
    - O1 (most common) and O139
  5. Dehydration (bacteria causes watery diarrhea)
    - Not toxins causing direct damage to cells
29
Q

How did pandemic cholera emerge?

A

Non-pathogenic V. cholerae strains acquired pathogenicity islands VPI-1 and VPI-2 and the vibrio toxin (CTX) to become pathogenic (via horizontal gene transfer)

30
Q

List the following for Legionaire’s Disease:
1. Causative agent
2. Reservoir
3. Transmission

A
  1. Legionella pneumophilia and other species
  2. Waterborne
  3. Aerosols from contaminated waters
31
Q

How did Legionella become pathogenic?

A
  • Ability to replicate in macrophages is due to virulence mechanisms it evolved to survive in its natural host (amoebae)
  • Selective pressures of living in amoebae drives the evolution of these virulence mechanisms (“training grounds”)
32
Q

Genetic diversity in viruses is driven by 2 ways. What are they?

A
  1. Mutation
  2. Genetic exchange
    - Recombination
    - Reassortment
33
Q

A major driver in seasonal variation of influenza is _____.

A

antigenic drift

34
Q

What is antigenic drift in influenza? How does it result in decreased immunity?

A
  • Point mutations in the surface glycoprotein hemagglutinin (HA)
  • Epitopes on the HA are lost –> reduces antibody recognition –> decreased immunity
35
Q

Why is the conservation of receptors in viruses a problem?

A
  • Conserved within different animal species
  • Receptors are almost identical and few mutation on the viral proteins may result in spillover
36
Q

Explain the H7N9 emergence.

A
  • March 2013: Chinese authorities reported identification of a novel zoonotic avian influenza A
  • Outbreaks occurred in waves
  • Linked to live bird markets
  • Transmission: exposure to infected poultry and contaminated environment
  • No sustained human-to-human transmission
37
Q

How did H7N9 become a human virus?

A

Virus initially only recognized avian sialic acid receptors (α-2,3 linkage) but acquired the ability to bind to human sialic acid receptors (α-2,6 linkage)

38
Q

H7N9 is a new virus that resulted from _____.

A

multiple reassortment events of 3 different influenza viruses

39
Q

When does reassortment occur?

A
  • When segmented RNA viruses co-infect a cell
  • Results in new virions with mixed segments
40
Q

Answer the following for Western equine encephalitis virus:
1. How is it transmitted?
2. Where are current infections localized?
3. What is the virus a result of?

A
  1. Mosquitoes
  2. Argentina and Uruguay
  3. Recombinant virus from an ancestral Sindbis virus-like virus and an ancestral Eastern equine encephalitis virus-like virus
41
Q

Diagram the evolution of SARS-CoV-2.

A

Emerging Infectious Diseases (BIOL 325) (16 decks)

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