Viral Respiratory Infections Flashcards Preview

Parasitology/Virology > Viral Respiratory Infections > Flashcards

Flashcards in Viral Respiratory Infections Deck (79):
1

What family is Rhinovirus in?

Picornovirus family

2

What is the major disease caused by Rhinovirus?

Common cold (rhinitis)

3

How is rhinovirus transmitted?

Airborne, person to person

4

Why does rhinovirus preferentially infect nasal epithelium?

Prefers the cooler temperature of nasopharynx (33) than internal body temp (37)

5

What is the structure of the virion of Rhinovirus?

Non-enveloped, single strand RNA virus
VP1, VP2, VP3 make up capsid
Has IRES (internal ribosome entry site)

6

Why is there no vaccine for rhinovirus?

Too many epitopes of the capsid proteins, gives >100 different subtypes

7

What is the funtion of IRES?

Internal ribosome entry site
In front of each gene, ribosome finds it and starts translation

8

What are the steps of replication of Rhinovirus?

Attaches
Endocytosed in vesicle
Uncoats and releases RNA into cytoplasm
RNA translated in *cytoplasm* with host ribosomes (targeted to IRES)
Long polyproteins get cleaved by proteases
New vesicles are formed with new viral RNA
Virions form and are released by cell lysis

9

What is the host response to Rhinovirus infection?

Induction of chemokines and cytokines that recruit inflammatory cells
Airways respond by contracting, increasing in mucus, increasing inflammation

10

What family is Influenza virus in?

Myxovirus - specifically orthomyxoviridae

11

What are major difference between orthomyxoviridae (influenza) and paramyxoviridae (parainfluenza, measles)?

Ortho - nuclear replication, segmented -sense RNA
Para - cytoplasmic replication, non-segmented -sense RNA

12

What is the most pathogenic type of influenza? (A, B, or C)

A

13

How many segments are in the influenza virion?

8 segments

14

How are strains of influenza named?

Type/Place/Number of isolate/Year (Major type of HA and NA)
Example: A/California/07/2009 (H1N1)

15

What is the mode of transmission of influenza?

Aerosols, direct contact

16

What are the steps of replication of influenza virus?

HA binds to sialic acid on surface of cell
Virus is endocytosed and endosome acidified
*Acidic environment* causes conformational change in HA, causing it to fuse with membrane and release viral RNA into cytoplasm
Viral RNA goes to nucleus for replication
Viral RNAs exported from nucleus and translated
New virions made, bud from cell

17

What cells does influenza primarily infect during infection?

Ciliated cells
Less cilia = less mucus, higher titer virus, more infected cells

18

What is antigenic drift?

Minor year to year variation that occurs by random mutations in HA and NA

19

What is antigenic shift?

Major reassortment of gene segments that leads to novel viral allele combination and can lead to increased virulence

20

What family is Parainfluenza in?

Paramyxoviruses

21

What disease do Parainfluenza type 1, 2, and 3 cause?

Croup

22

What is a major similarity and a major difference in the virion/genome of Influenza and Parainfluenza?

Similarity: Both contain own polymerase that starts working to replicate virus right when it enters cell

Difference:
- Influenza requires acidic pH for fusion, parainfluenza requires neutral pH
- Influenza replicates in nucleus, parainfluenza in cytoplasm

23

What are the steps of replication of parainfluenza?

Virus binds sialic acid on surface of cells
Fusion occurs at neutral pH
Viral mRNA is transcribed in cytoplasm
Proteins are processed in ER and Golgi
Virions bud from cell

24

How does parainfluenza block innate immune response?

Like other paramyxoviruses, can inhibit induction of interferon or degrade the proteins that turn on interferon induced genes

25

What is the mode of transmission of Parainfluenza?

Aerosols, direct contact

26

What virus causes most serious pediatric respiratory infections?

RSV (respiratory syncytial virus)

27

What is the structure of the virion of RSV and metapneumovirus?

Nucleocapsid in lipid envelope
Also contains own polymerase (like influenza and parainfluenza)

28

Where do RSV and metapneumovirus replicate (cytoplasm or nucleus)?

Cytoplasm

29

Which is more severe, RSV or metapneumovirus?

RSV

30

What is the cause of the severity of RSV?

Starts in nasopharynx and disseminates to lower respiratory tract
Causes necrosis and destruction of bronchiolar epithelium and ciliated epithelial cells
Causes influx of inflammatory cells, mucus production, and cell debris that can block bronchioles

31

What animal causes SARS?

Civet cats
(civets got from bats, which are the reservoir)

32

What animal causes MERS?

Camels? Bats? Dunno

33

What protein does SARS bind to?

ACE2 on surface of ciliated epithelial cells

34

What protein does MERS bind to?

DPP4 on surface of clara and type 2 alveolar cells

35

What is the major determinant of immunogenicity in SARS and MERS?

Spike protein

36

What virus is the major cause of the common cold?

Rhinovirus

37

What virus is the second most common cause of the common cold?

Coronaviruses

38

Where does Rhinovirus preferentially infect?

Nasal mucosa due to lower temperature (optimal for RhV growth)

39

What receptor does Rhinovirus bind to?

ICAM1

40

How does Rhinovirus cause the symptoms in the nasal mucosa?

Induces production of bradykinin - causes vasodilaiton
Induces production of IL-8 - causes influex of PMNs and vascular permeability

41

What is the typical clinical presentation of rhinovirus infectoin?

Sneezing, rhinitis, nasal obstruction, sore throat
NO fever

42

What is the incubation period of rhinovirus?

24-72 hours

43

When do rhinovirus infections typically peak?

Two peaks: fall and late spring

44

How is rhinovirus transmitted?

Direct contact or respiratory droplets

45

What is the treatment for rhinovirus?

No approved anti-virals
Supportive care (hydration, antihistamines)
Intranasal corticosteroids
Zinc, echinacia
No vaccine (>100 serotypes)

46

What is the common term for acute laryngotracheobronchitis?

Croup

47

What is the leading viral cause of croup?

Parainfluenza viruses (usually PIV-1 or PIV-3)

48

What is the hallmark of croup?

inflammation and subsequent narrowing of subglottic region of trachea, causing "barking cough"

49

In what populations is parainfluenza virus more of a problem?

Young children, elderly, immunocompromised
May need intubation

50

What is the clinical presentation of croup?

Barking cough
Stridor, hoarseness, fever

51

What is the incubation period of croup?

1-7 days

52

How is croup transmitted?

Direct contact, respiratory droplets

53

What is the seasonality of PIV-1?

Autumns of odd numbered years

54

What is the seasonality of PIV-2?

Annual in autumn (only mild disease)

55

What is the seasonality of PIV-3?

Annual in spring and early summer

56

How is croup diagnosed?

Naso-pharyngeal specimen submitted for viral culture, antigenic testing, or PCR
Can do neck x-ray to assess tracheal narrowing ("steeple sign")

57

What is the therapy for croup?

No approved anti-virlas
Supportive care
Monitor airway
No vaccine

58

What respiratory disease is leading cause of childhood hospitalizations for acute respiratory infection?

Bronchiolitis

59

What is most common viral cause of bronchiolitis?

Respiratory Syncytial Virus (RSV)

60

How does RSV cause airway obstruction?

Infects nasopharynx and spreads to bronchiolar epithelium, including pneumocytes
Syncitia formation promoted by F (fusion) protein
Necrosis and inflammation leads to small airway obstruction
Severe disease can cause respiratory failure

61

What is the clinical presentation of bronchiolitis?

Fever, wheezing, increased respiratory effort, apnea

62

What is the incubation period of bronchiolitis?

4-6 days

63

When is the peak of transmission of RSV?

Winter: January- February

64

What are risk factors for development of severe RSV?

Premature birth (<12 weeks
Chronic pulmonary disease
Congenital heart disease
Immunodeficiency
Neurological disease
Congenital/anatomic airway defect

65

What are long term complications of RSV?

Asthma or atopic disease

66

How is RSV diagnosed?

Nasal specimen for culture
Antigenic testing
PCR
Chest x-ray and pulse ox to assess pneumonia and oxygenation status

67

What is the treatment for RSV?

Supportive care +/- steroids and bronchodilators
Severely ill have been treated with Ribavirin
Palivizumab: monoclonal antibody against RSV, approved for immuneprophylaxis for high-riskinfants

68

What area of the respiratory tract does influenza effect?

All of it

69

Does an antigenic shift result in pandemic or epidemic?

Pandemic

70

Does and antigenic drift result in pandemic or epidemic?

Epidemic

71

What is the clinical presentation of influenza?

Abrupt *fever*, severe headache, severe myalgia, severe malaise
+ Respiratory symptoms
+/- GI symptoms

72

What is the incubation period of influenza?

3 days

73

What is the seasonality of influenza?

Winter in respective hemispheres
constant low level in tropics

74

What age group is predominantly afflicted by influenza?

Elderly, immunocompromised, young

75

What is the shape of the mortality curve of seasonal influenza?

U shape (skew to older)

76

What is the shape of the mortality curve of pandemic influenza?

W shape (young otherwise healthy adults get infected)

77

How is influenza diagnosed?

Rapid antigen tests
PCR

78

What are current influenza vaccines directed at (what portion of virus)?

HA portion of virus

79

What are current drugs used to treat influenza?

Neuraminidase inhibitors
- Oseltamivir
- Zanamivir
- Peramivir