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Microbiology > L26-27: Viral Respiratory Tract Infections > Flashcards

L26-27: Viral Respiratory Tract Infections Flashcards

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1
Q

Where do more viral respiratory tract infections occur and why?

A

Upper respiratory tract due to cooler temperature – viruses tend to replicate better at 33-35 degrees C

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2
Q

Why can viral damage predispose patients to bacterial super-infections?

A

Mucociliary escalator is interrupted and immune system is weakened

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3
Q

Symptoms of the common cold

A

Rhinitis (inflammation of nasal mucosa) and pharyngitis (sort throat) but no high fever, LRT involvement, or respiratory distress

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4
Q

Incidence of the common cold

A

2-3 times per year in adults and 6-8 times per year in children; peak in spring and fall

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5
Q

Complications of the common cold

A

Otitis media, sinus infections, exacerbation of asthma (especially rhinovirus C)

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6
Q

Viruses associated with common cold

A

Rhinovirus, coronavirus, adenovirus, coxsackievirus

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7
Q

Characteristics of rhinoviruses

A

Picornavirus family member, non-enveloped, +ssRNA genome; three types are A, B and C and hundreds of serotypes

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8
Q

How are rhinoviruses transmitted?

A

Through direct contact with nasal secretions, large droplets, and contaminated fomites; extremely low inoculum needed for infection

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9
Q

How do rhinoviruses cause disease?

A
  • -Virus infects nasal epithelial cells by entering and replicating
  • -Virus causes damage inside the epithelial layer of tissue, leading to clear fluid outpouring
  • -More and more cell damage as virus spreads
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10
Q

Why don’t we have vaccines for rhinoviruses?

A

There are more than 100 serotypes (but immune response can be long-lasting to particular serotype)

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11
Q

Characteristics of coronaviruses

A

Enveloped, +ssRNA genome, named for their sun-shaped appearance (non-SARS cause the common cold)

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12
Q

How is temperature preference different for non-SARS and SARS coronaviruses?

A

SARS viruses replicate better at body temperature, which is why they cause severe lower respiratory tract infection, while non-SARS viruses replicate at cooler temperatures

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13
Q

How does transmission of the non-SARS coronaviruses occur?

A

Through large droplets

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14
Q

Characteristics of adenoviruses

A

Adenovirus family, non-enveloped, dsDNA genome, fibers protruding from them are toxic to cells; no seasonal pattern of disease

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15
Q

Most common respiratory disease-causing serotypes for adenovirus

A

1, 2 and 5

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16
Q

What other illnesses can be caused by adenoviruses?

A

Pharyngoconjunctival fever (conjunctivitis, pharyngitis, and fever); more severe things such as croup, bronchiolitis, pneumonia; gastrointestinal disease

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17
Q

Characteristics of coxsackieviruses

A

Enterovirus subfamily of picornaviruses, non-eneloped, +ssRNA, fast replication, able to survive low pH conditions of GI tract

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18
Q

How are coxsackieviruses transmitted?

A

Fecal-oral route (occur more at daycare centers)

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19
Q

What else can coxsackieviruses cause?

A

Herpangina, hand-foot-&mouth disease

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20
Q

Hand-foot-&-mouth disease

A

Caused by coxsackievirus, symptoms include fever, vesicular lesions on hands and feet and oral areas; most frequent in children

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21
Q

Herpangina

A

Caused by coxsackievirus, symptoms include abrupt onset of fever, small vesicles on soft palate; most frequent in children 1-7 years

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22
Q

What other viruses can cause the common cold?

A

Influenza viruses (B and C), respiratory syncytial virus, and parainfluenza virus

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23
Q

What is croup?

A

Acute laryngotracheobronchitis, symptoms due to swelling in subglottic region of larynx

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24
Q

Symptoms of croup

A

Fever, distinct brassy cough comparable to seal’s bark, inspiratory stridor, narrowing of air shadow of trachea in radiograph (“steeple sign”), common cold-like symptoms

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25
Q

Why is croup more worrisome in younger children?

A

The younger the child, the smaller the airway, and less obstruction can occur before it conflicts with oxygen transfer

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26
Q

How do treatments differ based on whether a child has stridor at rest?

A

No stridor at rest –> humidified air, hydration

Stridor at rest –> oxygen, epinephrine, glucocorticoids

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27
Q

Types of parainfluenza virus

A

Type 1 is most common cause of acute croup, type 2-3 can also cause croup

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28
Q

Characteristics of parainfluenza virus

A

Paramyxovirus family, helical nucleocapsid, envelope with hemagglutinin and neuraminidase, -ssRNA genome

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29
Q

Transmission of parainfluenza virus

A

Large droplets and direct contact

30
Q

Incubation period of parainfluenza virus

A

2-10 days

31
Q

Symptoms of influenza

A

Myalgia, headache, fever, shaking chills, cough peaking between 3-5 days of illness, fatigue

32
Q

Pneumonia

A

Inflammation of the lung parenchyma leading to abnormal gas exchange; symptoms include fever, chills, cough, pleural chest pain, increased respiratory rate, wheezes/crackles, hypoxia and cyanosis

33
Q

2 types of pneumonia associated with Influenza virus

A

Primary Influenza virus pneumonia (usually Influenza A) and bacterial Influenza-associated pneumonia

34
Q

Primary Influenza virus pneumonia

A

Caused by Influenza A usually, occurs more in children and ages 40+, symptoms begin mild and 1-4 days later more severe symptoms occur such as increased cough, tachypnea, dyspnea, acute respiratory distress

35
Q

Sputum Gram stain for primary Influenza virus pneumonia

A

Abundant PMN cells without significant number of bacteria

36
Q

Who is at risk for complication due to Influenza?

A

Children, 65+, pregnant women and women up to 2 weeks postpartum (also certain medical conditions)

37
Q

Bacterial Influenza-associated pneumonia

A

Usually occurs one week after Influenza symptoms begin – flu symptoms lessen then increased cough, return of fever, and respiratory distress; Gram stain may contain bacterial cause

38
Q

What are the main bacterial causes of bacterial Influenza-associated pneumonia?

A

S. pneumoniae, S. aureus and H. influenzae (also N. meningitidis, other streps, and Gram- Bacillus)

39
Q

Characteristics of Influenza virus

A

Orthomyxovirus, segmented -ssRNA viral genome, enveloped, two important proteins are hemagglutinin (H) and neuraminidase (N)

40
Q

Hemagglutinin (H)

A

Responsible for attachment, agglutinates RBC, important target for immune response

41
Q

Neuraminidase (N)

A

Cleaves sialic acid, responsible for virion release and spread, important target for immune response

42
Q

Antigenic drift

A

Small changes in H and N driven by point mutations made by polymerase during replication, causes significant epidemiological changes every 2-3 years (becomes completely different from original parent virus and this is the reason for changes in vaccines)

43
Q

Antigenic shift

A

Large changes in H and N driven by reassortment of two viruses, occurs only with co-infection of the same cell, risk for pandemics (virus may end up so different immune system can’t identify it)

44
Q

Where does reassortment occur?

A

Ex. Birds and humans have a hard time infecting each other, but when they interact with pigs the viruses can go back and forth between species (pig is like mixing vessel)

45
Q

Differences between flu viruses A, B, and C: genome segments

A

A and B = 8 segments

C = 7

46
Q

Differences between flu viruses A, B, and C: host range

A 
A = humans, swine, avian, equines, marine mammals
B = humans only
C = humans and swine
47
Q

Differences between flu viruses A, B, and C: disease severity

A 
A = often severe
B = occasionally severe
C = usually mind
48
Q

Differences between flu viruses A, B, and C: epidemic potential

A 
A = often causes epidemics, pandemics
B = causes outbreaks and occasional epidemics
C = limited outbreaks
49
Q

Differences between flu viruses A, B, and C: antigenic change

A

All types capable of antigenic drift, only A capable of antigenic shift

50
Q

Antiviral treatments for Influenza

A
  1. Ion channel blockers

2. Neuraminidase inhibitors

51
Q

Ion channel blockers

A

Includes Amantadine and Rimantadine, blocks replication prior to genome release (M2 channel blockers), only effective against Influenza A and currently viruses are resistant to these drugs

52
Q

3 types of neuraminidase inhibitors

A
  1. Zanamivir (oral inhalation)
  2. Oseltamivir (oral)
  3. Peramivir (intravenous)
53
Q

Neuraminidase inhibitor

A

Inhibit virion release and spread, active against A and B – causes clumping of virus on the surface of cells

54
Q

Inactivated Influenza vaccines (IIV)

A

Formaldehyge-inacticated viruses, intramuscular (typical) or intradermal to patients at high risk/chronic medical conditions

55
Q

Live attenuated Influenza vaccine (LAIV)

A

Attenuated viruses, intranasal, can be given to healthy, non-pregnant persons

56
Q

Recombinant Influenza vaccine (RIV)

A

Hemagglutinin protein, intramuscular, can be given from 18-49 y/o

57
Q

Vaccine production methods

A

Classic method = production in embryonated chicken eggs
Novel method = production in mammalian cells (MDCK cells)
Recombinant vaccine = egg-free system that is best for immunocompromised patients or those with egg allergies

58
Q

Trivalent vaccines

A

2 Influenza A + 1 Influenza B strains

59
Q

Quadrivalent vaccines

A

2 Influenza A + 2 Influenza B strains

60
Q

Chemoprophylaxis for Influenza virus

A

Daily dose of anti-viral for duration of flu season in the community, given to those at high risk or when poor match between vaccine and circulating strains

61
Q

Characteristics of SARS coronavirus

A

Coronavirus family, enveloped, +ssRNA genome, more resistant to environmental factors

62
Q

Progression of SARS

A

Fever, malaise, and myalgia with dry cough and shortness of breath, most severe cases can cause adult respiratory distress syndrome (ARDS) and death

63
Q

Transmission

A

Fecal-oral, close contact, and aerosol routes

64
Q

Middle East Respiratory Syndrome (MERS)

A

Similar to SARS, spreading around Middle East

65
Q

Bronchiolitis

A

Inflammation of the bronchioles, symptoms include expiratory wheezing, nasal flaring, air trapping, subcostal retractions, and variable fever – often severe in infants due to small size of tissues

66
Q

Respiratory Syncytial Virus (RSV)

A

Most common cause of bronchiolitis and pneumonia in children <1 y/o, paramyxovirus family, enveloped, -ssRNA genome, highly infectious

67
Q

Transmission of RSV

A

Inhalation of large droplets or direct contact with respiratory secretion

68
Q

Ribavirin treatment for RSV

A

Aerosolized, guanosine analogue that inhibits nucleotide biosynthesis/mRNA capping and promotes hypermutation of the genome – only indicated for severe LRT RSV infections

69
Q

Prevention of RSV

A

Passive immunoprophylaxis for preemies and <2 y/o with chronic lung disease

70
Q

Agents for RSV passive immunoprophylaxis

A

Palivizumab (chimeric human-mouse monoclonal anti-RSV antiboy) and RSIG (pooled human immunoglobin)

71
Q

Other viruses that cause respiratory illness

A

Avian Influenza, Cytomegalovirus, measles and Varicella-Zoster (with pneumonia as a complication)

Microbiology (20 decks)

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