Influenza

Question 1

What shift in viral DNA can be caused by mutations due to the sun’s radiation?

Answer 1

Antigenic shift

Question 2

What are features of the influenza virus?

Answer 2

-From orthomyxoviridae family
-RNA virus
-3 types
>IfA (infects mammals and birds)
>IfB and IfC (infects humans only)

Question 3

What are some surface proteins of the influenza virus?

Answer 3

> Haemagglutinin (H) - facilitates viral entry to host cell. 18 different H antigens with H1-3 in humans
Neuraminidase (N) - enables new virion to be released from host cell. 11 different N antigens

Question 4

Discuss antigenic drift?

Answer 4

• Is the mechanism of genetic variation within the virus
• Small ongoing point mutations in genes coding for antibody binding sites
• Antigenic properties change = immune system doesn’t combat virus as well
• Causes vaccine mismatch and worsened epidemics

Question 5

Discuss antigenic shift?

Answer 5

• Abrupt major virus change = new H/N combinations
• Enables flu strain to jump from one animal species to another
• 2 or more different viral strains combine to form new subtype
• Reassortment of virus gene segments
• Leads to PANDEMICS

Question 6

What is a well known example of a pandemic that took place?

Answer 6

H1N1 virus in 2009/10

Question 7

How is seasonal flu and pandemic flu different?

Answer 7

Seasonal flu

• occurs every winter
• affects 10-15%
• usually unpleasant but not life threatening

Pandemic flu

• occurs sporadically
• affects 25%+
• more serious/complications

Question 8

What are the requirements for a pandemic to take place?

Answer 8

> human pathogenicity
‘new’ virus (antigenic shift)
efficient human-human transmission

Question 9

Discuss avian influenza:

• strains
• transmissions
• fatality rate

Answer 9

• Many strains but few affect humans (eg H5N1, H7N9)
• Direct contact with infected birds. Occasionally close human-human contact. Not through properly cooked foods
• Fatality rate high (eg 60% H5N1)

Question 10

What are clinical features of Influenza?

Answer 10

> Around 2-4d incubation
Fever lasting around 3d. Likely to be tired and have chills too
2 more of: cough (sore throat, rhinorrhoea), myalgia, headache, malaise
Predominantly systemic symptoms
Less commonly: nausea, vomiting, diarrhoea

Question 11

WHO definition of influenza like illness?

Answer 11

• Fever (>38 degrees) and
• Cough
• Onset in last 10d

Question 12

What is the transmission of Influenza virus?

Answer 12

> Airborne: person-person by large droplets (>5 microns)

>Contact: direct (person-person) or indirect (person-fomite-person)

Question 13

How long does it take for influenza virus to shed?

Answer 13

First 4d of illness. Longer in children and immunocompromised

Question 14

How long does virus survive on surfaces?

Answer 14

• 24-48h on non-porous surfaces

- 8-12h on porous surfaces (eg tissue)

Question 15

What are high risk groups for complicated influenza?

Answer 15

• Neurological, hepatic, renal, pulmonary, chronic cardiac disease
• DM
• Severe immunosuppression
• > 65y
• Pregnancy (plus <2w post partum)
• Children <6m
• Morbid obesity (BMI at least 40)

Question 16

What are common respiratory complications of influenza virus? What 3 organisms can present as part of complications?

Answer 16

• Acute bronchitis
• Secondary bacterial pneumonia (4-5d after flu start)

Microbiology

• S. pneumoniae
• S. aureus
• H. influenzae

Question 17

What is an uncommon respiratory complication of influenza virus?

Answer 17

Primary viral pneumonia

• common in avian influenza cases
• rapid respiratory failure in 48h
• mortality >40% in 7d

Question 18

What is an uncommon cardiac complication of influenza virus?

Answer 18

Myocarditis/pericarditis

Question 19

What is an uncommon neurological complication of influenza virus?

Answer 19

• Transverse myelitis/GBS

- Myositis and myoglobinuria

Question 20

What is encephalitis lethargica? What are clinical features

Answer 20

• There was a pandemic of this disease in 1918, suspected to be associated with Influenza A (serology).
• 25% mortality
• Can lead to postencephalitic

Features

• fever, headache
• external opthalmoplegia
• lethargy
• sleep reversal

Question 21

Diagnosis of Influenza virus?

Answer 21

>Viral nose and throat swabs/VTS (pcr)
>CXR (eg pneumonia)
>Blood culture
>Pulse oximetry - SpO2 <92% need ABG and O2
>Resp rate***
>U and E
>FBC, CRP

Question 22

What are the two main antiviral therapy drugs? (examples of neuraminidase inhibitors)

Answer 22

> Oseltamivir - oral

• common side effects: n+v, abd pain, diarrhoea
• less common side effects: headache, hallucinations, insomnia
• usually 1st line

> Zanamivir - inhaled/nebulised/IV
-rare side effect - bronchospasm

Question 23

What are other antiviral therapy drugs?

Answer 23

• Peramivir (neuraminidase inhibitor)

- Favipiravir (viral RNA polymerase inhibitor)

Question 24

What is the guidance for antiviral therapy when a woman is pregnant/breastfeeding?

Answer 24

> As normal for pregnancy

>Oral oseltamivir for breastfeeding

Question 25

When do immunocompetent and immunocompromised patients become non-infectious?

Answer 25

Immunocompetent:
-24h after last flu symptoms or when antiviral therapy completed

Immunocompromised:
-Treat as case by case

Question 26

What is used for protection when dealing with patients with suspected/proven flu?

Answer 26

> Surgical face mask
Plastic apron
Gloves
Washing hands afterwards

Question 27

What is used for seeing patients receiving Nebuliser, NIV etc with aerosolised virus?

Answer 27

FFP3 respirator mask

Question 28

Why is the yearly flu vaccine contraindicated in those with egg allergy?

Answer 28

Grown in allantoic cavity of chick embryos

Question 29

How is the yearly flu vaccine delivered? What is a side effect?

Answer 29

> IM injection

>Only adverse effect established is sore arm

Question 30

Why should healthcare workers have vaccinations?

Answer 30

> Protect themselves and family
Reduce risk to ‘at risk’ patients
reduce absence from work during influenza outbreak