Influenza

Question 1

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

Answer 1

northern = Dec-Feb
Southern = Jun-Aug

Question 2

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

Answer 2

every 11 years

sunspot activity - radiation

Question 3

What is the suns influence in terms of influenza?

Answer 3

radiation may cause mutations leading to antigenic shifts in viral RNA

Question 4

What year was Spanish flu?

Answer 4

1918/19

Question 5

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

Answer 5

A = mammals and birds

B and C = only humans

Question 6

Describe the influenza virus

Answer 6

RNA virus
8 segment genome
Orthomyxoviridae family

Question 7

Name the 2 surface proteins on the influenza virus

Answer 7

H and N

Question 8

H surface protein role

Answer 8

Facilitates viral attachment and entry to host cell

Question 9

N surface protein role

Answer 9

Enables new virion to be released from host cell

Question 10

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

Answer 10

18

1-3 in humans

Question 11

How many different N antigens are there?

Answer 11

11

Question 12

Explain antigenic drift

Answer 12

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

Question 13

Explain antigenic shift

Answer 13

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

Question 14

3 requirements for a pandemic

Answer 14

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

Question 15

Differences between seasonal and pandemic flu

Answer 15

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

Question 16

How does Avian flu spread?

Answer 16

direct contact with dead or alive infected birds

rarely person to person contact eg carers

Question 17

Clinical features of flu

Answer 17

abrupt fever of up to 41 degrees for 3 days

plus 2 of: cough, myalgia, headache, malaise

Question 18

Who definition of influenza like illness

Answer 18

fever - >38 degrees

cough - within last 10 days

Question 19

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

Answer 19

severe acute respiratory illness

Question 20

3 modes of transmission for flu

Answer 20

Airborne - person to person by large droplets >5microns

Contact - direct or indirect (fomite)

Question 21

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

Answer 21

first 4 days of illness

young and immunocompromised

Question 22

Virus survival on porous and non-porous surfaces

Answer 22

non porous: 24-48hours

porous: 8-12 hours

Question 23

7 risk factors for complicated influenza

Answer 23

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

Question 24

Common respiratory complications of influenza

Answer 24

acute bronchitis

secondary bacterial pneumonia

Question 25

Causative organisms of secondary bacterial pneumonia

Answer 25

staph aureus strep pneumonia H. influenza

Question 26

Less common complications of flu

Answer 26

Guillian Barre myocarditis primary viral pneumonia

Question 27

Briefly explain encephalitis lethargica

Answer 27

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

Question 28

6 diagnosis and investigations for flu

Answer 28

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

Question 29

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

Answer 29

urgent CXR

Question 30

When should you start antiviral therapy?

Answer 30

ASAP and within 48 hours of onset

Question 31

Name 2 neuraminidase inhibitors

Answer 31

oseltamivir | zanamivir

Question 32

Route of admission and side effects of oseltamivir

Answer 32

oral | nausea, vomit and diarrhoea

Question 33

Route of admission and side effects of zanamivir

Answer 33

inhaled | occasional bronchospasm

Question 34

Name 2 other antiviral therapies and briefly describe them

Answer 34

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

Question 35

When do immunocompetent adults become non infectious?

Answer 35

24 hours after last symptom, or after last dose of antiviral | whichever is longer

Question 36

When do immunocompromised or young children become non infectious?

Answer 36

consider each case separately

Question 37

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

Answer 37

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

Question 38

Describe briefly the seasonal flu vaccine

Answer 38

prepared each year depending on most likely | circulating strains and is trivalent - 2 type A and 1 B

Question 39

How is the seasonal flu vaccine prepared?

Answer 39

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

Question 40

volume and route of administration of flu vaccine

Answer 40

0.5ml | arm im

Question 41

3 reasons why healthcare workers should get flu vaccines

Answer 41

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