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I&I WC1 > Transmission of viruses > Flashcards

Transmission of viruses Flashcards

This deck covers the lectures about respiratory-, fecal-oral- and sexual transmission of viruses

1
Q

What are the three ways of respiratory virus transmission?

A
  • (In)direct contact through inoculation of fomites
  • Large droplets land on mucosa of person in close proximity
  • Aerosols are inhaled and deposited in respiratory tract
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2
Q

What can be said about the INF load during respiratory transmission for:
- Donor
- Interface
- Recipient

A
  • Donor: high INF load
  • Interface: stability
  • Recipient: low INF load
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3
Q

What are the characteristics of the donor during respiratory transmission? (5)

A
  • High viral load
  • Replication in URT
  • Induction of production of mucus
  • Induction of clinical signs
  • Host immune responses
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4
Q

What factors influence the interface during respiratory transmission? (5)

A
  • Stability/survival in aerosols
  • Temperature
  • Relative humidity -> influences environmental survival pathogen
  • Air ventilation (inside) and air movement (outside)
  • UV radiation
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5
Q

What are the characteristics of the recipient during respiratory transmission? (4)

A
  • Low infectious dose
  • Size of virus-containing aerosols
  • Tissue/cellular tropism
  • Host immune responses
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6
Q

What kind of experiments/data generates evidence of the airborne transmission of respiratory viruses? (5)

A
  • Outbreak reports
  • Experimental infection of humans
  • Animal experiments
  • Data on exhaled breath
  • In-vitro experiments
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7
Q

Describe an example of experimental infection of humans about airborne transmission of RSV

A

Young adults were divided into three groups to measure airborne transmission
- Cuddlers: caring for the baby in the usual manner
- Touchers: volunteers touched the contaminated surfaces
- Sitters: Exposed by sitting at a distance of more than 6 ft

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8
Q

Why are animal experiment useful to study airborne transmission of influenza virus? (3)

A
  • Animals are susceptible to natural infection
  • Respiratory disease and lung pathology similar to humans
  • Patterns of virus attachment similar to humans
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9
Q

What are the host differences during influenza A infection between avian- and human flu? (3)

A
  • Target: intestinal tract vs. upper airways
  • Different receptor
  • Temperature: 41C vs 33C
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10
Q

Which questions can one ask when studying generations and collection of respiratory viruses from the air? (3)

A
  • Which respiratory viruses can be found in the air? For how long? Are they still infectious?
  • Which particles contain virus? Large droplets or small aerosols?
  • What is the viral load in the air?
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11
Q

What are the three phases of person-to-person transmission?

A
  • Phase 1: Generation, aerosolization and exhalation
  • Phase 2: Transport via air; droplets
  • Phase 3: Inhalation, deposition and infection
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12
Q

What are the three phases of the research agenda for respiratory transmission routes?

A
  • Transmission routes
  • Animal experiments
  • In-vitro experiments
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13
Q

What are the parameters for respiratory emission? (3)

A
  • Aerosols
  • Droplets
  • Monodisperse/heterogeneous
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14
Q

What are the parameters for the interface/environment? (4)

A
  • Salinity
  • Mucus
  • Temperature/humidity
  • Evaporation
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15
Q

Respiratory transmission: What are the parameters for the recipient? (4)

A
  • (new) samplers
  • Air-liquid interface cultures
  • Presence of mucus
  • Infectious dose
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16
Q

What is the definition of fecal-oral human-to-human transmission?

A

Transmission of a pathogen from the host (acutely ill or chronic carrier) to a susceptible human (recipient) via the fecal-oral route

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17
Q

Which viruses follow the fecal-oral human-to-human transmission route? (5)

A
  • Enteric adenovirus
  • Hepatitis A virus
  • Norwalk virus
  • Poliovirus and other enteroviruses
  • Rotavirus
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18
Q

What makes rotavirus special?

A

Lower incidence, higher mortality

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19
Q

Which pathways of the fecal-oral route cause contamination of food? (4)

A
  • Flies/Fomites
  • Field/Floors
  • Fluids
  • Fingers
20
Q

Which pathways of the fecal-oral route can infect the new host directly? (3)

A
  • Field/Floors
  • Fluids
  • Fingers
21
Q

Fecal-oral: What causes contamination of the environment? (2)

A
  • Vomiting
  • Diarrhea
22
Q

What is the biggest problem in water contamination?

A

Heavy rainfall causing wastewater overflow

23
Q

What are examples of water contamination by wastewater overflow? (3)

A
  • Swimming water
  • Irrigation water
  • Growing water for oysters
24
Q

What causes the increase in norovirus contamination in the fecal-oral transmission route via contaminated water-infected food?

A

Climate change

25
Q

True or false: ‘Norovirus is an unstable virus’

A

False. Norovirus is really stable. Contaminated objects can cause infections up to two weeks after contamination

26
Q

What are important factors for fecal-oral transmission? (3)

A
  • Host factors
  • Virus factors
  • Environmental factors
27
Q

Name examples of host factors important for fecal-oral transmission (3)

A
  • Gut microbiome
  • Receptor expression in intestinal tract
  • Human behaviour (hygiene, agriculture, food preference)
28
Q

Name examples of virus factors important for fecal-oral transmission (3)

A
  • Shedding in stool
  • Stability in the environment
  • Intestinal tract niche adaptation
  • Pathogenicity
29
Q

What is meant with ‘pathogenicity’ of viruses causing GI-tract infections?

A

Ability to cause diarrhea

30
Q

Name examples of environmental factors important for fecal-oral transmission (2)

A
  • Climate
  • Environmental microbiome
31
Q

Is replication in the intestine necessary for shedding in the stool?

A

No

32
Q

Which virus has liver tropism?

A

Hepatitis E

33
Q

Which virus uses multiple routes for human-to-human transmission?

A

Hepatitis E

34
Q

Which routes does Hepatitis E virus use for human-to-human transmission?

A
  • Fecal-oral
  • Blood-borne
35
Q

What are characteristics of viruses that transmit via the fecal-oral route? (4)

A
  • Viruses have to shed via the stool
  • Clinical symptoms can increase the likelihood of fecal-oral transmission
  • Stability of viruses in the environment
  • Viruses have to adapt to the (harsh) conditions of the intestinal tract
36
Q

What are characteristics of the harsh environment of the GI-tract? (5)

A
  • Acidity of the stomach
  • Bile salts
  • Antiviral defenses (proteolytic enzymes, secretory IgA)
  • Mucus and gut mobility
  • M cells
37
Q

What is the function of bile salts in the GI-tract?

A

Destruction of lipid envelops of many viruses

Most GI tract viruses don’t have an envelop to subvert the bile salts

38
Q

What is the function of M cells?

A

Sampling of microorganisms and antigens for delivery to DCs in PP

39
Q

Cell culture models are needed to study viruses to obtain information about … (4)

A
  • General virology
  • Food and environmental virology
  • Clinical medicine
  • Epidemiology
40
Q

What is the pitfall of cell culture models to study viruses that transmit via the fecal-oral route?

A

They replicate poorly in cell-culture

41
Q

What are the characteristics of norovirus? (6)

A
  • RNA virus, capsid, no lipids
  • Fecal shedding extremely high levels
  • Low infectious dose
  • Stability outside host
  • Asymptomatic infections
  • Fecal-oral transmission
42
Q

What indicates a possible role of the microbiome in norovirus infection?

A

Norovirus replicates in B cells in the presence of bacteria

43
Q

Name a structure of bacteria that can stabilize virus particles in the environment

A

LPS from gram-negative bacteria

44
Q

Which animals can be used to study fecal-oral transmission? (4)

A
  • Mini pigs
  • Dogs
  • Zebrafish
  • Mice
45
Q

Why are in vivo experimental models build?

A

To find better models to investigate antivirals

46
Q

What is another way by which norovirus can be transmitted?

A

Spread through saliva

47
Q
A

I&I WC1 (25 decks)

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