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
Why is it so bad to get influenza + superinfection?
Synergistic effect: you get so much infiltrate & its bad news
26
How do you diagnose influenza?
PCR
27
How is influenza treated?
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
How is influenza prevented?
Influenza vaccine
29
What are the 2 types of vaccines? Who can get them? Who can't get them?
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
What causes death from influenza?
1. exacerbation of underlying illness 2. bacterial superinfection 3. sudden severe disease (fulminant) after initial mild illness
31
What is Guillain Barre syndrome?
**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