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Influenza Flashcards

1
Q

In what months does seasonal influenza occur?

A

Seasonal influenza occurs during winter months:

  • Dec to Feb in Northern hemisphere
  • Jun to Aug in Southern hemisphere
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2
Q

Why do epidemics of influenza occur every roughly 11 years?

A

Epidemics occur every 11 years which is thought to be linked to sunspot activity that causing antigenic shifts in viral RNA (mutation)

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3
Q

What kind of virus is influenza?

A

Is an RNA virus with 8 segment genome:

  • Orthomyxoviridae family
  • Three main groups
    • Influenza A
      • Mammals and birds
    • Influenza B
      • Only humans
    • Influenza C
      • Only humans
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4
Q

What are the 3 main groups of influenza and what animals do they infect?

A
  • Influenza A
    • Mammals and birds
  • Influenza B
    • Only humans
  • Influenza C
    • Only humans
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5
Q

From what family of viruses is influenza from?

A
  • Orthomyxoviridae family
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6
Q

What are the surface proteins of influenza?

A
  • 18 different H antigens (H1-3 in humans)
    • Haemagglutinin (H)
      • Facilitates viral attachment and entry to host cell
  • 11 different N antigens
    • Neuraminidase (N)
      • Enables new virion to be released from host cell
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7
Q

What is the function of haemagglutinin?

A
  • Facilitates viral attachment and entry to host cell
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8
Q

What is the function of neuraminidase?

A
  • Enables new virion to be released from host cell
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9
Q

What is antigenic drift?

A
  • Is mechanism of genetic variation within virus
  • Occurs continuously over time, small on-going point mutations in genes coding for antibody binding sites
  • May change the antigenic properties and eventually immune system will not combat virus well
  • Causes worse than normal epidemics and vaccine mismatch
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10
Q

What are consequences of antigenic drift?

A
  • Causes worse than normal epidemics and vaccine mismatch
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11
Q

What is antigenic shift?

A
  • Is abrupt major changes in virus resulting in new H/N combinations
  • Enables flu strain to jump from one animal species to another
  • Process by which two or more different strains of virus combine to form new subtype, creating new H/N combincations (reassortment)
  • With new antigenic properties can lead to pandemics due to population being unprotected
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12
Q

What are consequences of antigenic shift?

A
  • With new antigenic properties can lead to pandemics due to population being unprotected
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13
Q

Compare and contrast seasonal flu and pandemic flu in terms of when it occurs, incidence and severity?

A
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14
Q

What are pandemic requirements?

A
  • Human pathogenicity
  • ‘New’ virus (antigenic shift), creating susceptible population
  • Efficient person-person transmission
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15
Q

How can you describe the incidence of pandemics over the year?

A

Incidence of pandemics is still a wave due to being worse in winter

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16
Q

What is avian flu?

A

Refers to disease caused by infection with avian (bird) influenza

Only a few strains affect humans, spreads through direct contact with infected birds that are either dead or alive

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17
Q

What is the clinical presentation of influenza?

A
  • Abrupt fever up to 41oC which lasts 3 days (range 1-5 days)
  • Plus 2 or more of
    • Cough, myalgia, headache, malaise
  • Predominance of systemic symptoms
  • Less common symptoms
    • Nausea, vomiting, diarrhoea
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18
Q

What is the WHO definition of an influenza like illness (ILI)?

A
  • Fever and
  • Cough
  • Onset within last 10 days
  • If requires hospitalisation is defined as severe acute respiratory infection (SARI)
19
Q

What does ILI stand for?

A

Influenza like illness

20
Q

What does SARI stand for?

A

Severe acute respiratory infection

21
Q

What are the ways influenza can be transmitted?

A
  • Airborne
    • Person to person by large droplets (>5 microns)
  • Contact
    • Direct (person to person)
    • Indirect (person to fomite to person)
22
Q

What is virus shedding?

A
  • Refers to expulsion and release of virus following successful reproduction during host-cell infection
23
Q

When does virus shedding of influenza occur?

A

Virus shedding occurs in first 4 days of illness (range is 1 to 7 days):

  • Refers to expulsion and release of virus following successful reproduction during host-cell infection
  • Longer in young children and immunocompromised
24
Q

What is the virus survival time of influenza on non-porous and porous surfaces?

A
  • 24-48 hours on non-porous surfaces
  • 8-12 hours on porous surface such as tissue
25
What are some risk factors (high risk groups) for complicated influenza?
* Neurological, hepatic, renal, pulmonary and chronic cardiac disease * Diabetes mellitus * Severe immunosuppression * Age over 65 years * Pregnancy (including up to two weeks post-partum) * Children under 6 months of age * Morbid obesity (BMI ≥40)
26
What are some complications of influenza?
* Common * Acute bronchitis * Secondary bacterial pneumonia * Less common * Primary viral pneumonia * Myocarditis/pericarditis * Transverse myelitis/Guillain-Barre * Myositis and myoglobinuria
27
Severity assessment of secondary bacterial pneumonia from influenza uses what score to asses severity?
CURB65 score
28
Describe the CURB65 score?
* **_C_**onfusion * **_U_**rea \>7mmol/l * **_R_**espiratory rate \>30mm * **_B_**lood Pressure (diastolic \<60 or systolic \<90) * \>65 years of age Risk of death in next 30 days increases as CURB65 score increases
29
When should patients with influenza get an urgent chest x-ray?
Patients with “flu symptoms and fever for \>4 days” should have an urgent chest x-ray
30
How is influenza diagnosed?
* Viral nose and throat swabs (molecular detection/PCR flocked swabs)
31
What investigations are done for influenza?
* Chest x-ray * Pneumonitis/pneumonia/ARDSS * Blood culture * Pulse oximetry * Respiratory rate * U&Es, FBC, CRP
32
When should antivrial therapy be used for influenza?
Use ASAP and within 48 hours of symptoms onset
33
What are the different kinds of antiviral therapy for influenza?
* Oseltamivir * Oral administration * Dose if over 13 years is 75mg every 12 hours for 5 days * Adverse effects * Common – Nausea, vomiting, abdominal pain, diarrhoea * Less Common – Headache, hallucinations, insomnia and rash * Zanamivir * Inhaled or IV administration * Dose if over 12 years is 10mg inhaled daily for up to 10 days * Adverse effects * Rare - occasional bronchospasms
34
Describe the lines of treatment for influenza?
1st line - oseltamivir 2nd line - zanamivir
35
Other than oseltamivir and zanamivir, what are some other antiviral therapies?
* Peramivir * Neuroaminidase inhibitor * IV infusion for uncomplicated influenza * Favipiravir * Viral RNA polymerase inhibitor * Oral * Baloxavir marboxil * Endonuclease inhibitor * One single dose
36
What is the pregnancy guidelines for treatment of influenza?
* Antivirals are recommended * Oseltamivir remains first line option
37
What is the breastfeeding guidance for influenza treatment?
* Current guidance is oral oseltamivir
38
When does somone with influenza become non-infectious?
Immunocompetent adult: * 24 hours after last flu symptoms (fever and cough) * Or when anti-viral therapy completed * Whichever is longer Immunocompromised adults and young children: * Consider each case separately
39
What protection against influenza can healthcare staff use?
* Surgical face mask * Plastic apron * Gloves * Wash hands after any examination
40
What kind of administration is the seasonal influenza vaccine?
Intramuscular injection
41
How is the season influenza vaccine prepared?
* Prepared from viruses considered to most likely be circulating in forthcoming Winter * Grown in chick embryos * Chemically inactivated and purified, trivalent vaccines * Containing 2 type A and 1 type B subtype viruses So cannot be used with egg allergy
42
How many types of influenza does the seasonal vaccine contain?
* Containing 2 type A and 1 type B subtype viruses
43
Why should healthcare workers be vaccinated against influenza?
* To protect themselves and families * Reduce the risk to at risk patients * Reduce absence from work during influenza surge activity

Medical Ethics & Law (52 decks)

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