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Medical Microbiology > Respiratory Viruses > Flashcards

Respiratory Viruses Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What is an URTI?

A

Upper respiratory tract infections (URTI)

Acute infection involving nose, paranasal sinuses pharynx & larynx

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2
Q

What is an LRTI?

A

Lower respiratory tract infection (LRTI)

Acute infection involving the airways and lungs

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3
Q

What region is infected in Rhinitis?

A

Nose

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4
Q

What are the symptoms of Rhinitis?

A

Sneeze
Watery/purulent discharge
Nasal obstruction

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5
Q

What region is infected in Pharyngitis?

A

Pharynx

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6
Q

What are the symptoms of Pharyngitis?

A

Pharyngeal inflammation

Red throat and or exudates

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7
Q

What region is infected in Croup?

A

Subglottic trachea

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8
Q

What are the symptoms of Croup?

A

Hoarseness
Barking cough
Inspiratory stridor

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9
Q

What region is infected in tracheobronchitis?

A

Trachea and larger bronchi

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10
Q

What are the symptoms of tracheobronchitis?

A

Cough, coarse rhonchi, mucus hyper-secretion

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11
Q

What region is infected in bronchiolitis?

A

Small bronchi and bronchioles

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12
Q

What are the symptoms of bronchiolitis?

A

Tachypnea, wheezing, hyper-resonance to percussion

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13
Q

What region is infected in viral pneumonia?

A

Lungs, especially alveoli

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14
Q

What are the symptoms of viral pneumonia?

A

Cough, fatigue, fever, shortness of breath, chest pain

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15
Q

What are the common causes of the common cold?

A

Rhinoviruses

Coronaviruses

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16
Q

What are the less common causes of the common cold?

A 
Influenza viruses
Parainfluenza viruses
Enteroviruses
Adenoviruses
RSV
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17
Q

What is the common cause of croup?

A

Parainfluenza viruses

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18
Q

What are the less common causes of croup?

A

Influenza viruses

RSV

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19
Q

What is the common cause of bronchiolitis?

A

RSV

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20
Q

What are the less common causes of bronchiolitis?

A

Influenza viruses
Parainfluenza viruses
Adenoviruses
Rhinoviruses

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21
Q

What is the common cause of influenza-like illness?

A

Influenza viruses

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22
Q

What are the less common causes of influenza-like illness?

A

Parainfluenza viruses

Adenoviruses

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23
Q

What are the common causes of viral pneumonia?

A

Influenza viruses
RSV
Adenoviruses

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24
Q

What are the less common causes of viral pneumonia?

A

Parainfluenza viruses
Enteroviruses
Rhinoviruses
Coronaviruses

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25
Q

When do RTIs usually occur?

A

RTIs occur typically late autumn to end winter

Peaks may vary for particular viruses

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26
Q

Why do RTIs peak in autumn/winter?

A 
Drop in temperature
Rise in humidity
Re-opening of schools
Emotional depression (SAD)
Increased indoor activities
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27
Q

What are the main vectors for RTIs?

A

School children

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28
Q

Describe the pathogenesis of an RTI

A

Virus enters Respiratory Tract
Absorption to ciliated epithelium via specific receptor
Viral replication
Hit and Run strategy
Host defences activated
high levels interferon α, IL–2, IL-6, and (TNF)-α

Possible secondary bacterial infection
NK cells and Macrophages activated
Fever and systemic symptoms
Recovery & cytotoxic T cell/antibody production

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29
Q

What family do the Human Parainfluenza Viruses (HPIV) belong to?

A

Paramyxoviridae

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30
Q

What are the two genera of HPIV?

A

Respirovirus (serotypes HPIV-1 and HPIV-3)

Rubulavirus (serotypes HPIV-2 and HPIV-4a and b)

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31
Q

Which serotype of HPIV is the most severe (esp. in young children)?

A

HPIV-3

32
Q

Describe the disease spectrum for HPIV

A

Subclinical to respiratory collapse

33
Q

How long is the incubation period for HPIV?

A

2-4 days

34
Q

Why is the incubation period so short?

A

The disease is found where it infects, so the virus does not need to spread through the body to cause symptoms

35
Q

What does HPIV-1 and 2 cause?

A

Croup in very young, and milder RTIs

75% infected by age 5

36
Q

What does HPIV-3 cause?

A

Severe bronchiolitis & pneumonia /severe croup

80% infected by age 4

37
Q

What does HPIV-4 cause?

A

Mild URT infection

38
Q

How long is the shedding period for HPIV?

A

3-10 days

39
Q

How is HPIV transmitted?

A

Transmission via direct inoculation or large particle aerosols

40
Q

Does reinfection occur with HPIV?

A

Yes, reinfection common (with reduced disease), esp. with URTI

41
Q

Describe the epidemiology of HPIV

A

HPIV-1 biennial /autumn
HPIV-2 biennial/autumn
HPIV-3 annual/spring
HPIV-4 less well characterised

42
Q

What are the risk factors for HPIV?

A 
Malnutrition
Overcrowding
Vitamin A deficiency
Lack of breastfeeding
Smoking
43
Q

What family does Respiratory Syncytial Virus (RSV) belong to?

A

Paramyxoviridae

44
Q

What are the genera of RSV?

A

Pneumovirus - subtypes A and B

45
Q

How is RSV transmitted?

A

Hands and fomites>droplets

46
Q

Describe the epidemiology of RSV

A

Peaks between December and March

Annual epidemics November to April

47
Q

Describe the disease spectrum of RSV

A

Mild cold to bronchiolitis
Most common viral LRTI in very young & elderly
Rare in neonates

48
Q

What are the risk factors for RSV bronchiolitis?

A 
Incidence highest in urban areas
Premature birth, low birth weight congenital heart disease, CF, IS
Lower socioeconomic status
Being male
> 2 smokers in household
> 5 people in household
Elderly and transplant patients
49
Q

Describe the immunopathogenesis for RSV bronchiolitis?

A

RSV is not cytopathic. Immune response to RSV infection results inepithelial damage and cellular desquamation.

Inflammatory changes in the lung cause narrowing of airway producing clinical symptoms of bronchiolitis

RSV can also cause asthma exacerbations in older children

50
Q

What family does Human Metapneumovirus (hMPV) belong to?

A

Paramyxoviridae

51
Q

Describe the disease spectrum of hMPV

A

URTI and LRTI very similar to RSV, less severe
Immunocompromised > risk severe disease
Seroprevalence 100% by 5 years
Recurrent infections throughout life

52
Q

Describe the epidemiology of hMPV

A

Annual epidemics late winter, early spring
Coincides/overlaps with RSV season
Sporadic infection year round

53
Q

What is the method of transmission for hMPV?

A

Direct /close contact with respiratory secretions

54
Q

How is adenovirus characterised?

A

Direct /close contact with respiratory secretions

55
Q

Describe the features of adenoviruses

A

Double stranded DNA
80nm, non-enveloped icosahedron
Fibre projecting from 12 vertices
2 Antigens: Group common & Type specific

56
Q

How many serotypes of human adenovirus are there?

A

> 51

57
Q

What family does Rhinovirus belong to?

A

Picornaviridae

58
Q

Describe the features of rhinovirus

A

18-30nm, non-enveloped, icosahedral, +ssRNA
Optimal growth 33˚C, acid labile

Causes 40% URTI.
Droplet transmission
Epidemiology- peaks late spring & autumn
2-3 day incubation, URTI 7days, virus shedding for 3 weeks
LRTI more common in children

59
Q

How many serotypes of Rhinovirus are there?

A

> 100

60
Q

Describe the features of Coronaviruses

A

80-200nm diameter
+ ssRNA

Envelope has 3 major glycoproteins:
S – Spike , E – Envelope, M - Membrane

Adult infection less common.
Can cause:
      - URTI Causes 2-10% common colds 
      - Mild, self-limiting disease
      - Enteric – typically in infants
61
Q

What is the incubation period for Coronaviruses?

A

3 days

62
Q

Which Coronaviruses have been identified as causing disease in humans?

A

Alpha coronaviruses 229E and NL63

Beta coronaviruses OC43

63
Q

What are the clinical features of SARS-CoV?

A

Fever >38 °C & myalgia
20% progressed to ARDS
30% mortality

64
Q

How is SARS-CoV transmitted?

A

Transmission by droplet & faecal contamination

65
Q

What is the natural reservoir for SARS-CoV?

A

Chinese horseshoe bat

66
Q

What is the intermediate (amplification) host for SARS-CoV?

A

Masked palm civet cat

67
Q

Describe the features of MERS-CoV

A

Novel Coronavirus identified June 2012 in Qatari national who died from severe
respiratory infection and renal failure

As of 2016, 1638 laboratory-confirmed cases reported with 587deaths

Family cluster in UK provides 1st evidence of human-to-human transmission

Zoonoses -originated in bats, transmitted to camels sometime in the distant past

Camels major reservoir for transmission to humans

Currently limited human – human transmission

Uses different cell receptor to SARS.

68
Q

What cell receptors does SARS-CoV use?

A

ACE2 in LRT

69
Q

What cell receptors does MERS-CoV use?

A

Dipeptidyl peptidase 4 (DPP4 or CD26) in URT and LRT

70
Q

What are the different techniques used to diagnose RTIs in the lab?

A

Cell culture
Immunofluorescence
Serology
PCR

71
Q

How is cell culture used to diagnose RTIs?

A

Infection induces typical cytopathic effect which can be seen under a microscope

e.g Parainfluenza viruses form large multinucleate syncytia

72
Q

How is immunofluorescence used to diagnose RTIs?

A

IF of viral antigen in cells from nasopharyngeal washes/cell culture isolates

73
Q

How is serology used to diagnose RTIs?

A

Complement fixation test

ELISA tests –specific IgG & IgM

74
Q

Why is PCR usually used to diagnose RTIs?

A 
Applicable to RNA or DNA viruses 
Rapid 
Multiplex PCR 
Products can be sequenced 
Improved patient management and disease surveillance
75
Q

How are RTIs prevented and treated?

A

Strict infection control
Supportive intervention
Stop antibacterial therapy

Children with Severe Viral Respiratory Disease

  • May use oxygen therapy / mechanical ventilation
  • For RSV, HPIV, hMPV Ribavirin aerosol may be used
  • For RSV administer Palivizumab monoclonal antibody

Medical Microbiology (13 decks)

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