Influenza Flashcards

1
Q

What months is influenza predominant in the northern and southern hemisphere?

A
northern = Dec-Feb
Southern = Jun-Aug
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2
Q

How often do severe epidemics occur? What is this linked to?

A

every 11 years

sunspot activity - radiation

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3
Q

What is the suns influence in terms of influenza?

A

radiation may cause mutations leading to antigenic shifts in viral RNA

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4
Q

What year was Spanish flu?

A

1918/19

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5
Q

What are the 3 main groups of virus and what species do they infect?

A

A = mammals and birds

B and C = only humans

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6
Q

Describe the influenza virus

A

RNA virus
8 segment genome
Orthomyxoviridae family

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7
Q

Name the 2 surface proteins on the influenza virus

A

H and N

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8
Q

H surface protein role

A

Facilitates viral attachment and entry to host cell

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9
Q

N surface protein role

A

Enables new virion to be released from host cell

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10
Q

How many different H antigens are there and which are found in humans?

A

18

1-3 in humans

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11
Q

How many different N antigens are there?

A

11

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12
Q

Explain antigenic drift

A

continual point mutations over time at antibody binding sites which may change the antigenic properties and lead to vaccine mismatch and the immune system not combatting the virus as well

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13
Q

Explain antigenic shift

A

Abrupt major change in virus leading to new H/N combinations leading to pandemics as the virus can go between species

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14
Q

3 requirements for a pandemic

A

efficient person to person transmission
human pathogenicity
new virus antigenic shift in a susceptible population

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15
Q

Differences between seasonal and pandemic flu

A

seasonal happens every year in the winter months with 10-15% affected and not life threatening
pandemics occur sporadically affecting 25%+ of population and more serious

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16
Q

How does Avian flu spread?

A

direct contact with dead or alive infected birds

rarely person to person contact eg carers

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17
Q

Clinical features of flu

A

abrupt fever of up to 41 degrees for 3 days

plus 2 of: cough, myalgia, headache, malaise

18
Q

Who definition of influenza like illness

A

fever - >38 degrees

cough - within last 10 days

19
Q

If hospitalisation is required what term instead of influenza like illness is used?

A

severe acute respiratory illness

20
Q

3 modes of transmission for flu

A

Airborne - person to person by large droplets >5microns

Contact - direct or indirect (fomite)

21
Q

When does viral shedding occur and what groups of people is it longer in?

A

first 4 days of illness

young and immunocompromised

22
Q

Virus survival on porous and non-porous surfaces

A

non porous: 24-48hours

porous: 8-12 hours

23
Q

7 risk factors for complicated influenza

A
diabetes mellitus 
children under 6 months 
morbid obesity 
severe immunosuppression
pregnancy and up to 2 weeks post partum 
>65
neurological, hepatic, renal, pulmonary and chronic cardiac disease
24
Q

Common respiratory complications of influenza

A

acute bronchitis

secondary bacterial pneumonia

25
Q

Causative organisms of secondary bacterial pneumonia

A

staph aureus
strep pneumonia
H. influenza

26
Q

Less common complications of flu

A

Guillian Barre
myocarditis
primary viral pneumonia

27
Q

Briefly explain encephalitis lethargica

A

1918 following flu pandemic
fever, headache, lethargy, postencephalitic parkinsonism
serology +ve flu A

28
Q

6 diagnosis and investigations for flu

A
viral nose and throat swabs - PCR 
blood culture 
CXR 
pulse oximetry 
respiratory rate 
U+E, FBC, CRP
29
Q

If a patient with flu has had flu symptoms and fever > 4 days and suspect secondary bacteria pneumonia what should you do?

A

urgent CXR

30
Q

When should you start antiviral therapy?

A

ASAP and within 48 hours of onset

31
Q

Name 2 neuraminidase inhibitors

A

oseltamivir

zanamivir

32
Q

Route of admission and side effects of oseltamivir

A

oral

nausea, vomit and diarrhoea

33
Q

Route of admission and side effects of zanamivir

A

inhaled

occasional bronchospasm

34
Q

Name 2 other antiviral therapies and briefly describe them

A

peramivir - neuroaminidase inhibitor given IV in complicated influenza
Favipir - viral RNA polymerase inhibitor given orally

35
Q

When do immunocompetent adults become non infectious?

A

24 hours after last symptom, or after last dose of antiviral

whichever is longer

36
Q

When do immunocompromised or young children become non infectious?

A

consider each case separately

37
Q

4 ways healthcare workers protect themselves when in contact with people with flu

A

wash hands after and use face-fit FFP3 respirator mask for those with a nebuliser
surgical face mask
plastic apron
gloves

38
Q

Describe briefly the seasonal flu vaccine

A

prepared each year depending on most likely

circulating strains and is trivalent - 2 type A and 1 B

39
Q

How is the seasonal flu vaccine prepared?

A

grown in allantoic cavity of chick embryos - CI in egg allergy

40
Q

volume and route of administration of flu vaccine

A

0.5ml

arm im

41
Q

3 reasons why healthcare workers should get flu vaccines

A

protect them and families
reduce risk to at risk patients
reduce absence from work during influenza surge activity