Influenza Flashcards
What shift in viral DNA can be caused by mutations due to the sun’s radiation?
Antigenic shift
What are features of the influenza virus?
Family
RNA or DNA virus - so mutation is quicker/slower
3 main groups and their respective susceptible groups
-From orthomyxoviridae family
-RNA virus
-3 types
>IfA (infects mammals and birds)
>IfB and IfC (infects humans only)
What are 2 surface proteins of the influenza virus?
What are their respective functions
> Haemagglutinin (H) - facilitates viral entry to host cell H1-3 in humans
> Neuraminidase (N) - enables new virion to be released from host cell
Discuss antigenic drift?
Define in 2 sentences
Antigenic drift causes… [2]
- 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 normal epidemics
Discuss antigenic shift?
Define in 2 sentences
Pathogenesis in 2 sentences
Causes… [1]
- 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
What is a well known example of a pandemic that took place?
H1N1 virus in 2009/10
How is seasonal flu and pandemic flu different?
Occurrence
Affected population
Complications
Seasonal flu
- occurs every winter
- affects 10-15%
- usually unpleasant but not life threatening
Pandemic flu
- occurs sporadically
- affects 25%+
- more serious/complications
What are the requirements for a pandemic to take place? [3]
> human pathogenicity
‘new’ virus (antigenic shift)
efficient human-human transmission
Discuss avian influenza:
- strains
- transmissions
- fatality rate
- 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)
What are clinical features of Influenza? Incubation period Fever characteristics + 2 more of 4 other features Predominance of x in presenting picture Less common symptoms 3
> Around 2-4d incubation
Abrupt fever lasting around 3d maybe assoc w chills
2 more of: cough (sore throat, rhinorrhoea), myalgia, headache, malaise
Predominance of systemic symptoms
Less commonly: nausea, vomiting, diarrhoea
WHO definition of influenza like illness? [3]
- Fever (>38 degrees) and
- Cough
- Onset in last 10d
What is the transmission of Influenza virus? [2]
> Airborne: person-person by large droplets (>5 microns)
>Contact: direct (person-person) or indirect (person-fomite-person)
How long does it take for influenza virus to shed?
First 4d of illness. Longer in children and immunocompromised
How long does virus survive on surfaces?
Porous vs non-porous
- 24-48h on non-porous surfaces
- 8-12h on porous surfaces (eg tissue)
What are high risk groups for complicated influenza? [5]
- Neurological, hepatic, renal, pulmonary, chronic cardiac disease
- DM, morbid obesity BMI >40
- Severe immunosuppression
- > 65y, <6m
- Pregnancy (third trim)
What are common respiratory complications of influenza virus? [2]
What 3 organisms can present as part of complications?
- Acute bronchitis
- Secondary bacterial pneumonia (4-5d after flu start)
Microbiology
- S. pneumoniae
- S. aureus
- H. influenzae
What is an uncommon respiratory complication of influenza virus?
Which type of influenza does it commonly appear?
Presentation [2 features]
Mortality rate
Primary viral pneumonia
- common in avian influenza cases
- rapid respiratory failure in 48h
- mortality >40% in 7d
What is an uncommon cardiac complication of influenza virus?
Myocarditis/pericarditis
What is an uncommon neurological/CNS complication of influenza virus? [3]
- Transverse myelitis/GBS
- Myositis and myoglobinuria
- Reye’s syndrome (children)
How is a diagnosis made in Influenza virus? [7]
>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
What are the two main antiviral therapy drugs? (2 examples of neuraminidase inhibitors)
ROA
SE
> 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
What are other antiviral therapy drugs? [2]
- Peramivir (neuraminidase inhibitor)
- Favipiravir (viral RNA polymerase inhibitor)
What is the guidance for antiviral therapy when a woman is pregnant/breastfeeding? [2]
> As normal for pregnancy
>Oral oseltamivir for breastfeeding
When do immunocompetent adult patients become non-infectious?
Immunocompetent:
-24h after last flu symptoms or when antiviral therapy completed
What is used for protection when dealing with patients with suspected/proven flu? [4]
> Surgical face mask
Plastic apron
Gloves
Washing hands afterwards
Why is the yearly flu vaccine contraindicated in those with egg allergy?
Grown in allantoic cavity of chick embryos
How is the yearly flu vaccine delivered? What is a side effect?
> IM injection
>Only adverse effect established is sore arm
