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MICBI Virology > L27 Viral infections of respiratory tract > Flashcards

L27 Viral infections of respiratory tract Flashcards

1
Q

The influenza virus is from the ____________ family. They are pleomorphic, with size 80-120mm with surface spikes.
They are enveloped/non-enveloped.

A

Othromyxoviridae

  • enveloped
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2
Q

For the Influenza virus, there is 8 segment virus and each segment corresponds to a gene.
___________ and __________ genes encode envelop glycoproteins, which induce immune response.
How many serotypes are there in each gene?

A

Haemagglutinin (HA) and Neuraminidase (NA)

18H and 11N subtypes

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3
Q

Other than genes that encode envelop glycoproteins, there are internal genes such as ______, NS, NP; PB1, PB2 and PA [RNA polymerase].

A

Matrix (M)

M1 (matrix protein), M2 (ion channel)

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4
Q

Name the most important influenza viruses and their reservoirs.

A
  1. Influenza A: human, birds, pigs
  2. Influenza B: mutate more slowly, affect almost exclusively human

(3. Influenza C: affect human, but usually with minor symptoms)

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5
Q

How do we express the nomenclature of an influenza virus?

A

Subtype/animal (if human, not specified)/ location / strain/year

e.g. A/Hong Kong/483/1997 (H5N1)

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6
Q

What is antigenic drift?

full definition

A

Accumulation of minor antigenic changes due to replication error of RNA polymerase, lacking proofreading ability

(HA/NA genes)

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7
Q

In which type(s) of influenza virus does antigenic drift occur?
What are the consequences?

A

Influenza A and B

  • Epidemic
  • usually types A H3N2, A H1N1, B
  • severe disease in high-risk groups, mild in healthy adults
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8
Q

What is the antigenic shift?

full definition

A

Gene reassortment of segments of the genome between 2 different strains, forming a new subtype with a mixture of surface antigens

(major change)

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9
Q

In which type(s) of influenza virus does antigenic shift occur?
What host?

A
  • Influenza A only

- Aquatic birds (avain) as a gene pool: prone to all subtypes

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10
Q

What are the consequences of antigenic shift? (2)

A
  • Pandemic production of a novel subtype with no immunity in the population
  • High mortality
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11
Q

What are the modes of transmission of the influenza virus? (2)

A
  1. Respiratory
    - droplet (>5 microns)
    - ?airborne (droplet nuclei <5 micrins) for new flu
  2. Direct contact
    - contact with respiration contaminated items (e.g. fomites)
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12
Q

Influenza virus can survive in the environment in up to 48h. Is it easily disinfected? Why? How?

A

Yes, because it is an enveloped virus.

  • By alcohol, soap and water/ hibiscrub/ >56 degrees
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13
Q

What is the common presentation of influenza virus infection?
- give examples of symptoms.

A

UTRI
(c.f. LRTI in avian flu)

  • abrupt onset of fever and chills, sore throat, dry cough, myalgia
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14
Q

Symptom-wise, how to differentiate Influenza and Common cold? (2)

A

Influenza

  • Fever
  • Dry cough

Common cold

  • Rhinorrhea
  • Nasal congestion
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15
Q

Which of the following about influenza is correct?
A. There is a higher viral load in younger children than adults
B. There is a longer duration of symptom presentation in younger children
C. Younger children may present with bronchiolitis, croup and vomiting.
D. Otitis media in adults
E. Sputum production in adults

A

D is incorrect; should be in children

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16
Q

What are the 2 main approaches to diagnose influenza?

A
  1. Specimen
    - Nasopharyngeal aspirate (NPA)
  2. Detection method
    - antigen detection: immunofluorescence, immunochromatography (rapid POCT)
    - RT-PCR (reverse transcription) as a standard test
  • cell culture rarely used
17
Q

Best location of obtaining a specimen
A. Oral, oropharynx
B. Nasopharynx
C. Nasal

Sequence from better location to least good.

A

Nasopharynx > Nasal > oral, oropharynx

18
Q

Which of the below has a higher viral yield?

A. Throat/nasal swab
B. Aspirate

A

B

19
Q

What are the precautions when taking a nasopharyngeal aspirate?

A
  • Require negative pressure
  • Wear PPE
    because it is an aerosol-generating procedure
20
Q

Name the 2 main classes of antiviral treatment for Influenza. (2)
Briefly describe their MOA.

A
  1. M2 channel blockers (e.g. amantadine)
    - inhibit uncoating
    - not used nowadays due to resistance, ineffective for influenza B
  2. Neuraminidase inhibitors
    - Neuraminidase (NA) cleaves terminal sialic acid residues on the host cell surface to release progeny viruses
  • Analogues of sialic acid to block the active site of NA
    > uncleaved sialic acid residues bind to HA
    > viral aggregation at the host cell surface
    > reduce virion release through secretion
    +/- promote production of pro-inflammatory cytokines
21
Q

Name 2 neuraminidase inhibitors and state their respective route of intake and frequency.
Possible side effects?

A
  1. Zanamivir (Relenza) - Inhaltion BD - bronchospasm
  2. Oseltamivir (Tamiflu) - Oral BD - GI symptoms
    (dosage adjustment required for Tamiflu, QD if Cr 10-30ml/min)
22
Q

Baloxavir is a new anti-flu agent.
It is a cap-dependent endonuclease inhibitor

A. it interferes with viral RNA transcription
B. it blocks viral replication
C. single lV dose is needed
D. better for >12 years old
E. No dose adjustment needed for CrCl >50 min/min
F. May cause GI upset or headache

A

Only C is wrong

Singal Oral dose

23
Q

What are the 2 main types of vaccination available for influenza?

A
  1. Inactivated vaccines (killed vaccine) [majority]

2. Live attenuated influenza vaccine (LAIV, FluMist) [one only]

24
Q

Content of inactivated vaccine for influenza?

A
  1. Trivalent (2 stains of Influenza A + 1 strain of B)

2. Quadrivalent (2 stains of Influenza A + 2 strains of B

25
Q

An inactivated vaccine for influenza has a short duration of protection - _________ months, thus vaccination has to be repeated each year.

WHO annual recommendation on vaccine composition is at which month for HK (Northern hemisphere)?

A

6-9 months

February

(Southern hemisphere: Sep)

26
Q

Efficacy of the inactivated vaccines of influenza depends on matching between ________ strains and ______ strains.

A

Vaccine strains and circulating strains

27
Q

Give 4 examples of high-risk groups of Influenza.

A
  1. Elderly >65
  2. Children from 6 months to 12y/o
  3. Pregnant women
  4. Chronic diseases: cardiovascular, lung, renal, children on long-term aspirin
  5. Healthcare workers
  6. Poultry workers
28
Q

Live attenuated influenza vaccine is administered via ___________ route, with similar composition (trivalent) as inactivated vaccine.
It is commonly recommended for ages?

A

Intranasal (東張西望!!)

- 2 years old to 49 years old

29
Q

Describe the seasonality of epidemics of influenza.

A

Both influenza A and B has consistent annual winter peak at temperate regions (e.g. US)

At tropical/subtropical regions (e.g. HK)

  1. Influenza A: 2 peaks: winter and summer
  2. Influenza B: 1-2 peaks: summer peak is less consistent
30
Q

What is the importance of knowing the seasonaility of influenza? (2)

A
  1. Timing of vaccination

2. Vaccine efficiacy: vaccine strain determined much ahead of the acutal epidemics

31
Q

What is the virus that causes barking cough in infants/adults? What family does this virus belong to?

A

Parainfluenza virus

Paramyxoviridae

32
Q

Which of the following about the Parainfluenza virus is correct?

A. It is an enveloped virus
B. (-)ssRNA virus, like Orthomyxoviridae
C. 5 serotypes present
D. Causes croup (laryngotracheobronchitis) in infants
E. Causes barking cough and sub-glottal swelling

How is it treated?

A

All of the above
- Supportive treatment

  • Croup: barking cough, SOB, hoarseness, stridor
33
Q

Other than Parainfluenza, name another virus from the Paramyxoviridae family. It is the most common cause of?

A

Respiratory syncytial virus (RSV)

  • MC cause of severe LRTI in infants
    e. g. bronchiolitis, bronchopneumonia, croup
34
Q

Which of the following about the Respiratory Syncytial Virus is correct?

A. It is an enveloped virus
B. (-)ssRNA virus
C. there are subgroups A and B
D. It cannot be prevented 
E. Adults presented with much milder symptoms compared to infants, e.g. ILI, bronchitis only
A

D is incorrect

- can be prevented by palivizumab (IgG against RSV)

35
Q

This virus most commonly causes pharyngitis, pharynconjunctival fever (red-eye fever), and pneumonia.
Name the virus and the family.

A

Adenovirus;

Adenoviridae

36
Q

Which of the following about the Adenovirus is incorrect?

A. It is an enveloped virus
B. dsDNA virus
C. has 7 subgenera
D. has >60 serotypes
E. MC serotypes are 3,4,7
A

A

- non-enveloped!

37
Q

Name the 2 viruses from the Picornaviridae family.

What do they commonly cause?

A
  1. Rhinovirus
  2. Enterovirus
  • URTI
38
Q

SARS-CoV is from which virus family?

What does it commonly cause?

A

Coronaviridae;

URTI (MC) but can also cause LRTI

MICBI Virology (9 decks)

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