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Year 3 - Infection > Influenza > Flashcards

Influenza Flashcards

1
Q

When does seasonal influenza occur?

A

Northern hemisphere = Dec-Feb

Southern Hemisphere = Jun-Aug

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2
Q

What relation doe s severe epidemics of influenza and increased sunspot activity have in common?

A

Occur every 11 years

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3
Q

What is the sun’s radiation role in influenza?

A

It is believed the sun’s radiation may cause mutations leading to antigenic shifts in viral RNA

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4
Q

What is vitamin D role in viral infections?

A

It is believed an increased level of Vitamin D helps to prevent viral infection

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5
Q

When did the Spanish flu pandemic occur?

A

1918-1919 = 20-100million deaths

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6
Q

When did the Asian flu pandemic occur?

A

1957-1958 = 1-1.5million deaths

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7
Q

When did the Hong Kong flu pandemic occur?

A

1968-1969 = 0.75-1 million deaths

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8
Q

When did the Swine flu pandemic occur?

A

2009-2010 = Approx 285,000 deaths

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9
Q

What type of virus is influenza?

A

RNA virus with an 8 segment genome

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10
Q

From what family is the influenza virus?

A

Influenza is an RNA virus from the Orthomyxoviridae family

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11
Q

What are the three main groups of influenza?

A

Type A = 1933
Type B = 1939
Type C = 1950

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12
Q

Which influenza infect mammals and birds?

A

Type A

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13
Q

Which influenza only infects humans?

A

Type B and Type C

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14
Q

What part of the influenza virus facilitates viral attachment and entry to host cell?

A

Haemagglutinin (H antigen)

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15
Q

How many different Haemagglutinin (H antigens) are there in influenza?

A

18 different Haemagglutin antigens (H1-3 in humans)

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16
Q

What part of the influenza virus enables new visions to be released from host cells?

A

Neuraminidase (N antigen)

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17
Q

How many different Neuraminidase (N antigens) are there in influenza?

A

11 different Neuraminidase antigens (N antigens)

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18
Q

What is Antigenic drift?

A

A mechanism of genetic variation within the virus cased by small on going point mutations in the genes coding for antibody binding sites

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19
Q

What is antigenic drift effect on the immune system?

A

Small mutations in the genes coding for antibody binding sites leads to the immune system not being able to combat the virus as well

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20
Q

What effect does antigenic drift have on vaccination?

A

Causes worse than normal epidemics & vaccine mismatch

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21
Q

A viruses with RNA or DNA genes more likely to undergo mutations?

A

RNA e.g. Influenza

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22
Q

Which strains does the influenza vaccine contain?

A

two A strains and one B strain - They are changed on a yearly basis dependant on the virus genetic drift

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23
Q

What allows one flu strain to jump from one animal species to another?

A

Antigenic shift

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24
Q

What is antigenic shift?

A

When two or more different strains of a virus combine to form a new subtype, resulting in new H/N combinations

“Reassortment of the virus’ gene segments”

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25
Q

What does antigenic shift often lead to?

A

Pandemics e.g. Bird flu/Swine Flu

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26
Q

The 2009/2010 influenza pandemic possessed which H/N antigens?

A

H1N1

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27
Q

Where did the 2009/2010 influenza pandemic originate?

A

In March 17th the first case as seen of the H1N1 influenza variant.

The first case in USA was identified March 28th

H1N1 was identified by the CDC April 14th

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28
Q

What is the main differences between seasonal flu and pandemic flu?

A

1) Seasonal = Every winter
Pandemic = Sporadic

2) Seasonal = 10-15% of the population
Pandemic = >25% of the population

3) Seasonal = Unpleasant but not life-threatening
Pandemic = More serious, more complications

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29
Q

What are the requirement of a pandemic?

A

1) Human pathogenicity
2) “New” virus (antigenic shift) - Susceptible population
3) Efficient person-person transmission

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30
Q

What are the characteristics of a pandemic?

A

“a new virus, a spike of cases outside the usual influenza season,
and a clear shift in the age distribution of illness and death”

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31
Q

What percentage of the UK population were infected with the H1N1 influenza virus in the 2009/2010 pandemic?

A

30% of the UK population

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32
Q

What percentage of the UK population infected with the H1N1 influenza virus in the 2009/2010 pandemic has mild symptoms?

A

82.7-82.9%

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33
Q

What percentage of the UK population infected with the H1N1 influenza virus in the 2009/2010 pandemic died?

A

0.1%-0.35% fatality rate (457 deaths)

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34
Q

What percentage of the UK population infected with the H1N1 influenza virus in the 2009/2010 pandemic required hospital treatment?

A

2%

35
Q

What percentage of the UK population infected with the H1N1 influenza virus in the 2009/2010 pandemic had complications?

A

15%

36
Q

What phenomenon did the 2009/2010 influenza pandemic follow?

A

A wave phenomenon

37
Q

H/N antigens of the 1997 avian flu?

A

H5N1 - fatality rate of 60%

38
Q

H/N antigens of the 2013 avian flu?

A

H7N9 - fatality rate of 36%

39
Q

How is avian flu transmitted?

A

1) Directly from birds, dead or alive (Not from consumption)

2) Occasional transmission via close human to human contact (e.g. caregivers)

40
Q

What are the current outbreaks of avian flu in China?

A

H7N9

41
Q

What are the current outbreaks of avian flu in Egypt?

A

H5N1

42
Q

What is the incubation period for influenza?

A

2-4days (Range 1-7days)

43
Q

Clinical features of influenza?

A

1) Abrupt fever up to 41oC (commonly 38-40oC) which last for three days (Range 2-5 days)
2) Two or more of: Cough, Sore throat/rhinorrhoea, myalgia, headache, malaise
3) Systemic symptoms
4) Less commonly: Nausea, vomiting, diarrhoea

44
Q

What are the characteristics of the fever in influenza?

A

Abrupt fever up to 41oC (commonly 38-40oC) which last for three days (Range 2-5 days)

45
Q

What is the WHO (2011) definition for influenza?

A
  • Fever >38oC; and
  • Cough

Onset within the last 10 days

46
Q

If influenza requires hospitalization what is it defined as?

A

Severe acute respiratory infection (SARI)

47
Q

Common symptoms in swine flu?

A

1) Typical fever >38oC
2) Sudden cough
3) Malaise, chills
4) Headache, sore throat, rhinorhoea, sneezing
5) Diarrhoea or stomach upset, loss of appetite
6 )Aching muscles, numb or joint pain

48
Q

How is Influenza transmitted?

A

Airborne = Person -> Person by large droplets >5 microns

Contact:

  • Direct (Person –> Person)
  • Indirect (Person –> fomite –> person)
49
Q

Virus shedding in influenza?

A
  • First 4 days of illness (Range from 1-7 days)

- Longer in young children and immunocompromised

50
Q

Virus survival in influenza?

A
  • 24-48 hours on non-porous surfaces

- 8-12 hours on porous surface e.g. tissue

51
Q

How far does a sneeze spread?

A

3 feet

52
Q

Who is at higher risk of complications in influenza?

A

1) Neurological hepatic, renal, pulmonary and chronic cardiac disease
2) Diabetes mellitus
3) Severe immunosuppression
4) >65 years old
5) Pregnancy - Including up to two weeks post partum
6) Children under 6 months
7) Morbid obesity (BMI >40)

53
Q

Common respiratory complications of influenza?

A
  • Acute bronchitis

- Secondary bacterial pneumonia (S pneumonia, S aureus, H influenza)

54
Q

Less common complications of influenza?

A

1) Viral pneumonia:
- Common in avian influenza (H5N1)
- Rapid respiratory failure
- Mortality >40% within 7 days

2) Myocarditis/pericarditis
3) Transverse myelitis/Guillain-Barre
4) Myositis and Myoglobunuria

55
Q

What was a big complication of the 1918 influenza pandemic?

A

Encephalitis lethargica

56
Q

How does encephalitis lethargica present?

A
  • Fever, headache
  • External ophthalmoplegia
  • Lethargy
  • Sleep reversal
  • 25% mortality
  • Postencephalitis parkinsonism
57
Q

How do we diagnose and investigate influenza?

A

1) Viral nose and throat swabs (PCR)
2) Chest radiograph - Pneumonitis/ARDS
3) Blood culture
4) Pulse oximetry - If SpO2 <92% need ABG and oxygen
5) Respiratory rate
6) U&E’s, FBC, CRP (Used to monitor recovery - Should halve in 4 days)

58
Q

If patients have flu symptoms and a fever for longer than 4 days what should be done?

A

An urgent chest radiograph to rule out secondary bacterial pneumonia

59
Q

What is used to to assess the severity of bacterial pneumonia?

A 
CURB-65:
C = Confusion 
U = Urea >7 mmol/L
R = Resp rate >30
B = BP (diastolic <60 or systolic <90)
65 = Age >65 years 
Risk of death in next 30days:
0 = 0.6%
1 = 3.2%
2 = 13%
3 = 17%
4 = 41.5%
5 = 57%
60
Q

What is the risk of death in the next 30 days if a CURB-65 score is 0 in bacterial pneumonia?

A

0.6%

61
Q

What is the risk of death in the next 30 days if a CURB-65 score is 1 in bacterial pneumonia?

A

3.2%

62
Q

What is the risk of death in the next 30 days if a CURB-65 score is 3 in bacterial pneumonia?

A

17%

63
Q

What is the risk of death in the next 30 days if a CURB-65 score is 4 in bacterial pneumonia?

A

41.5%

64
Q

What is the risk of death in the next 30 days if a CURB-65 score is 5 in bacterial pneumonia?

A

57%

65
Q

Treatments available for influenza virus?

A

Neuraminidase inhibitors:

  • Oseltamivir
  • Zanamivir
  • Peramivir

Viral RNA polymerase inhibitor:
- Favipiravir

66
Q

What dose is needed for Oseltamivir in influenza?

A

Oral - Over 13 years old = 75mg every 12 hours for 5 days

67
Q

What dose is needed for Zanamivir in influenza

A

Inhaled - Over 12 years old = 10mg daily for up to 10 days

68
Q

When should neuraminidase inhibitors be administered in flu?

A

ASAP, but within the first 48Hrs of symptom onset

In complicated disease should always be given

69
Q

What are the adverse effects of Oseltamivir (Tamiflu)?

A

Common: Nausea, vomiting, abdominal pain, diarrhoea

Less common: Headache, hallucinations, insomnia, rash

Cautions - Renal dosing

70
Q

What are the adverse effects of Zanamivir (Relenza)?

A

Rarely occasional bronchospasm

71
Q

Which influenza strain has a higher risk of oseltamivir resistance? What should be used instead?

A

H1N1, Zanamivir

72
Q

Which influenza strain has a lower risk of oseltamivir resistance?

A

H3N2

73
Q

What is the first line therapy in complicated influenza unless H1N1?

A

1st line = Oseltamivir

2nd line = Zanamivir if poor clinical response or if H1N1 strain

74
Q

In complicated influenza what is the 1st line therapy?

A

1st line = Oseltamivir

2nd line = Zanamivir if poor clinical response or if H1N1 strain

75
Q

What is the therapy of choice in influenza within pregnancy?

A

1st line = Oseltamivir

2nd line = Zanamivir if poor clinical response or if H1N1 strain

76
Q

What is the therapy of choice in influenza when breast feeding?

A
  • Only tiny amounts of Oseltamivir in milk

- Current guidance is – Oral Oseltamivir

77
Q

When does an individual become non-infectious after influenza?

A

Immunocompetent adult:
- 24hrs after last flu symptom
- Or when anti-viral therapy complete
Which ever is longer

Immunocompromised adults and young children:
- Case by case basis

78
Q

How can healthcare staff protect themselves against influenza?

A

Proven or suspected “flu”:

  • Surgical face mask
  • Plastic apron
  • Gloves
  • Wash hands after examination
  • Face-fit FFP3 respirator mask, eye protection and gown for though who are receiving a nebuliser
  • Seasonal flu vaccination
79
Q

Who cannot receive the seasonal flu vaccination?

A

Those who are allergic to eggs

80
Q

How is the seasonal flu vaccination administered?

A

A single 0.5ml intramuscular injection

81
Q

What are the complications of seasonal flu vaccine?

A
  • Sore arm

- Rare = Tissue infection due to bad hygiene

82
Q

Where is the flu vaccine grown?

A

Allantoic cavity of chick embryos

83
Q

Why should healthcare workers receive the seasonal flu vaccination?

A

1) To protect themselves and their families
2) To reduce the risk to “at risk” patients
3) To reduce absence from work during influenza “surge” activity

Year 3 - Infection (16 decks)

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