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MID II > Respiratory Viruses > Flashcards

Respiratory Viruses Flashcards

1
Q

What are the major causes of respiratory viral disease?

A

Influenza

Respiratory syncytial virus (RSV)

Also: parainfluenza, rhinovirus, coronavirus, enterovirus

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2
Q

What are the possible spectrum of diseases caused by viral respiratory illness?

A

Upper airway disease (runny nose, sore throat)

Bronchiolitis

Pneumonia

Acute respiratory distress syndrome (diffuse alveolar damage, respiratory failure)

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3
Q

Who is at highest risk for getting severe RSV disease?

A

Very young infants

Premature infants

Immunocompromised

Convenital heart or lung disease

** Almost everyone gets it by age 2, but it’s not always severe

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4
Q

What is the structure of RSV?

A

neg sense ssRNA, enveloped virus

Paramyxoviridae family (includes mumps, measles)

11 proteins in the genome, including F and G protein = surface glycoproteins, targets of immune response

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5
Q

What does the F protein in RSV do?

A

Fusion protein

Responsible for synctia formation: multinucleated giant cells

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6
Q

What does the G protein in RSV do?

A

Surface glycoprotein, mediates attachment

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7
Q

What is the pathogenesis of RSV?

A

Incubation period = 3-6 days, replicates in the cells of the upper airway, cna cause upper resp tract disease

Can spread to lower airway & cause croup, bronchiolitis, pneumonia, otitis media, apnea, wheezing

No viremia!

Duration of uncomplicated illness is 1-3 weeks

Immunity following infection is incomplete

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8
Q

What is the immune response to RSV?

A

Innate: surfactant, TLRs

Cell mediated immunity = antibodies against F and G protein

Pathology is due to the immune response

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9
Q

How is RSV diagnosed?

A

Clinical diagnosis

RTPCR

Viral culture = slow

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10
Q

How is RSV treated?

A

Supportive: O2, secretion management, monitor for apnea, intubation/ventillation if necessary

Bronchodilators, steroids – not really beneficial

Ribavirin – not used, not a good drug

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11
Q

How is RSV prevented?

A

Hand washing

Monoclonal antibody for high risk infants = palivizumab, targets F glycoprotein

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12
Q

Who is at risk to severe illness due to influenza?

A

Extremes of age

Pregnancy

Immunocompromised

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13
Q

What are the clinical manifestations of influenza?

A

ILI = influenza like illness – fever, chills, HA, myalgia, arthralgia, dry cough, nasal discharge

Young kids can get sepsis like syndrome, GI, croup, otitis media

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14
Q

What are complications of influenza?

A

Pneumonia

Bacterial super infection (S pneumo, S aureus, GAS)

Myocarditis

Encephalitis

Myositis

Reye syndrome (liver damage + encephalopathy)

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15
Q

How long is the incubation period of influenza? Duration of illness?

A

1-4 days incubation period

4-8 days of acute illness

1-2 weeks of convalescence (i.e. cough)

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16
Q

What is the structure of influenza virus?

A

neg sense ssRNA, enveloped

8 segments including HA and NA (which determine serotype)

17
Q

What does HA of influenza do?

A

Hemagglutinin: viral attachment

Think H for Hugs

18
Q

What dos NA of influenza do?

A

Neuroaminidas: Involved in viral budding from infected cells

Think N because it releases New viruses from cell

19
Q

How does influenza infect a new cell?

A

HA helps it bind target cell

Then endocytosis brings it into cell – this is an acidic pocket, which activates viral glycoproteins to allow release of viral materials

viral RNA dependent RNA pol transcribes + sense RNAs to make viral proteins

Host RNA polymerase makes new neg sense RNAs for new virions

Viral assembly

New viruses go to cell membrane & still attached until sialidase cleaves it –> released to infect other cells

20
Q

How long does viral replication occur? How long does viral shedding continue?

A

1-3 days of replicatoin

Shedding for 7-10 days

21
Q

What cells does influenza infect? What is the result?

A

Columnar epithelial cells of the respiratory tract

Result is epethelial destruction, increased mucous production, ciliarly stasis

22
Q

What is antigenic shift?

A

Slow change of viral surface antigens over time

Due to lack of proofreading of RNA polymerase

This is why not all viruses of the same strain are identical & you get resistance to vaccine/meds

23
Q

What is antigenic drift?

A

Sudden, rapid change i.e. H1 to h3

Responsible for pandemics

Due to reassortment of segments during viral packaging and release

24
Q

What is a pandemic?

A

When there’s sustained human to human transmission of influenza

25
Q

Why is it so bad to get influenza + superinfection?

A

Synergistic effect: you get so much infiltrate & its bad news

26
Q

How do you diagnose influenza?

A

PCR

27
Q

How is influenza treated?

A

Uncomplicated = supportive

Antiviral agents: reserved for high risk patients

Amantidine, rimantidine: block influenza A M2 channel, which promotes viral uncoating – no activity against influenza B. Give within 48 h of symptoms

Oseltamivir (tamiflu), zanamivir: Neuroaminidase inhibitors. Give within 72 h of symptoms

28
Q

How is influenza prevented?

A

Influenza vaccine

29
Q

What are the 2 types of vaccines? Who can get them? Who can’t get them?

A

TIV: trivalent inactivated – for anyone over age 6 months, no egg allergy

LAIV: live attenuated intranasal – 2-49 years old
Not if egg allergy, immunocompromised, taking aspirin, history of Guillain Barre syndrome, asthma, pregnant women, person in close contact with hospitalized bone marrow transplant recipients

30
Q

What causes death from influenza?

A
  1. exacerbation of underlying illness
  2. bacterial superinfection
  3. sudden severe disease (fulminant) after initial mild illness
31
Q

What is Guillain Barre syndrome?

A

Autoimmune disorder

Acute inflammatory demyelinating polyneuropathy of peripheral nervous system

Triggered by an acute infectious process

Presents as ascending paralysis

Treat wtih supportive care, plasmapheresis, IV Ig’s –> full recovery

MID II (22 decks)

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