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Infection > Influenza > Flashcards

Influenza Flashcards

1
Q

When does seasonal influenza occur?

A

Winter (dec-feb)

More severe epidemics every 11y

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2
Q

What vitamin is thought to help prevent viral infection?

A

Vit D

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3
Q

What kind of virus is influenza?

A

RNA virus

Of the orthomyoxviridae family

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4
Q

What are the main groups of influenza?

A

A
B
C

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5
Q

What are the surface proteins on the influenza virus?

A

Haemagglutinin (H) - facilitates viral attachment and entry into host cells (18 diff types)
Neuraminidase (N) - enables new virions to be released from host cells (11 diff types)

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6
Q

What is antigenic drift?

A

Genetic variation within virus
Causes epidemics
Due to small on-going point mutations in genes coding for Ab binding sites (minor changes in H and N) that does not alter the subtype
Leads to worse than normal epidemics & vaccine mismatch

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7
Q

What is antigenic shift?

A

Abrupt major chance in virus leading to new H and N combinations
Two different subtypes of virus enter same cell and there is mixing to form different combination
New antigenic properties –> population at risk and unprotected –> pandemics

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8
Q

What are the differences between pandemic and seasonal flu?

A

Pandemic occurs sporadically, affects 25% of pop or more and is more serious with more complications

Seasonal occurs every winter, affects 10-15% of population, and tends not to be lifethreatening

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9
Q

What are the requirements of a pandemic?

A

Human pathogenicity
New virus (antigenic shift)
Efficient person to person spread

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10
Q

What is the incubation period of the influenza virus?

A

2-4 days (range: 1-7)

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11
Q

What are the clinical features of influenza?

A

Abrupt fever (up to 41C) lasting 3 days (1-5) plus 2+ of: cough, myalgia, headache, malaise (sore throat, rhinorrhoea)

Less common symptoms: N/V, diarrhoea

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12
Q

What is the Who definition for an influenza like illness?

A

Fever (>38C) + cough

Onset within last 10 days

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13
Q

If influenza requires hospitalisation what is it called?

A

Severe, acute respiratory infection (SARI)

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14
Q

How is the influenza virus transmitted?

A

Airborne (large droplets >5microns), contact (direct - person to person or indirect (person-fomite-person)

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15
Q

What is viral shedding?

A

Repulsion and release of a virus after successful replication inside the host

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16
Q

When does viral shedding occur?

A

In the firsts 4 days of illness (range: 1-7 days)

But longer in children/immunocompromised

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17
Q

How long does the influenza virus survive on non-porous surfaces?

A

24-48h

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18
Q

How long does the influenza virus survive on porous surfaces?

A

8-12h

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19
Q

What are risk factors for complicated influenza?

A 
Neurological, pulmonary, cardio, renal or hepatic disease 
DM 
Severe immunosuppression 
Age >65 
Pregnancy (incl. 2 weeks post partum) 
Children <6m 
Morbid obesity (BMI >40)
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20
Q

What are the common complications of flu?

A

Acute bronchitis

Secondary bacterial pneumonia

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21
Q

When does secondary bacterial pneumonia appear?

A

4-5 days after flu

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22
Q

What microbes can cause secondary bacterial pneumonia?

A

S. pneumonia
Staph aureus
H. influenzae

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23
Q

What are less common complications of the flu?

A

Primary viral pneumonia
Myocarditis/pericarditis
Transverse myelitis/GB syndrome
Myositis/myoglobulinuria Encephalitis lethargica

24
Q

With which flu are you more likely to get primary viral pneumonia?

A

Human avian influenza (H5N1)
Leads to rapid respiratory failure within 48h
Very high mortality

25
Q

What is encephalitis lethargica?

A

Associated with serology +ve influenza A 1918 epidemic
Fever, headache, opthalmoplegia, lethargy, sleep reversal
May get post-encephalitic parkinsonism

26
Q

What investigations should you do in suspected flu?

A 
Viral nose &amp; throat swab (molecular detection/PCR)
CXR (?pneumonitis/pneumonia/ARDS)
Blood culture
Pulse oximetry if SpO2 <92% then do ABG
U&amp;E, FBC, CRP
27
Q

How should CRP change in recovering pneumonia?

A

Half in 4 days

28
Q

How do you investigate patients with suspected secondary bacterial pneumonia?

A

Patient with flu symptoms & fever >4 days should have urgent CXR
Measure severity with CURB65

29
Q

What is CURB65?

A 
Severity marker for pneumonia
Gives risk of dying in next 30 days 
C- confusion 
U - urea >7mmol/L
R- RR >30 
BP - diastolic <60, systolic < 90 
>65
30
Q

How do you treat uncomplicated flu?

A

Symptomatic Rx - e.g. paracetamol & antivirals if HIGH RISK

31
Q

How do you treat complicated influenza?

A

Admit to history & give antivirals

32
Q

When should you start antivirals?

A

Within 48h of symptom onset

33
Q

What antivirals do we use for flu?

A

Neuraminidase inhibitors -
Oseltamivir - 75mg every 12h x 5d (13y+)
Zanamivir - 10mg daily x 10d (12y+)

34
Q

What are the ADRs of oseltamivir?

A

Common - abdominal pain, NV, diarrhoea
Uncommon - headache, hallucinations, insomnia, rash
Careful of renal dosing

35
Q

What are the ADRs of zanamivir?

A

Rare - bronchospasm

36
Q

What antiviral is best in uncomplicated flu with a dominant circulating strain that has low ostelamivir resistance (e.g. A (H3N2) or B)?

A

Oseltamivir PO

37
Q

What antiviral is best in complicated flu with a dominant circulating strain that has low ostelamivir resistance (e.g. A (H3N2) or B)?

A

1st line: oseltamivir PO

2nd line: zanamivir INH/NEB/IV (if poor clinical response)

38
Q

What antiviral is best in uncomplicated/complicated flu with a dominant circulating strain that high risk of ostelamivir resistance (e.g. A (H1N1))?

A

Zanamivir INH

May NEB/IV in complicated

39
Q

What other antivirals can you use?

A

Peramivir - neuraminidase inhibitor

Favipiravir - RNA polymerase inhibitor

40
Q

How do you Mx flu in pregnancy/breast feeding?

A

Antivirals - oseltamivir or zanamivir

Both are safe in pregnancy and breast feeding

41
Q

When are people who have had flu considered non-infectious?

A

24h after last flu symptoms/when antiviral course complete

May be longer in immunocomp/kids

42
Q

How can healthcare workers protect themselves from flu?

A

PPE (masks, plastic apron, gloves)
Handwashing
Wear face fit mask if patient receiving nebuliser

43
Q

How are the seasonal flu vaccines prepared?

A

Consider most likely circulating viruses in forthcoming winter
Grown in allantoic cavity of chick embryo (CI in egg allergy)
Chemically inactivated and purified

44
Q

What does the seasonal flu vaccine contain?

A

Trivalent - 2 type A and 1 type B subtype viruses

45
Q

What is the dosage of the flu vaccine?

A

0.5ml IM

46
Q

What are the adverse effects of flu vaccine?

A

Sore arm

47
Q

When should people be vaccinated against flu?

A

From september to november

48
Q

What flu vaccine is given to kids?

A

Intranasal live vaccine
Given at 2-3y then annual after than

if immunocompromised will need injectable inactivated vaccine

49
Q

What are contraindications to the active intranasal flu vaccine?

A 
Immunocompromised
Age <2y
Current febrile illness/blocked nose/rhinorrhoea
Current wheeze/hx severe asthma
Egg allergy 
Pregnancy/breast feeding
Taking aspirin (risk of Reye's syndrome)
50
Q

What are SEs of the intranasal active flu vaccine?

A

Blocked nose/rhinorrhoea
Headache
Anorexia

51
Q

Who should be offered an annual flu vaccine?

A

Every >65 and those >6 months with:

  • Chronic respiratory disease (incl. asthmatics on inhaled steroids)
  • Chronic heart disease
  • Chronic kidney disease
  • Chronic liver disease
  • Chronic neurological dsiease
  • DM
  • Immunosupression due to treatment or disease
  • Asplenia/splenic dysfunction
  • Pregnant women
  • BMI >40
  • Health and social care staff
  • Those in residential homes
  • Carers of the elderly/disabled
52
Q

What kind of vaccine is the trivalent vaccine given to adults?

A

Inactived

53
Q

What are side effects of the flu vaccine?

A

Fever and malaise

54
Q

What are CIs to getting the inactive vaccine?

A

Egg allergy

55
Q

How long does the flu vaccine take to work?

A

10-14 days

Infection (22 decks)

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