Influenza Flashcards
When are the influenza months?
Dec - Feb (North)
Jun - Aug (South)
When do more severe influenza epidemics take place?
Every 11 years - sunspots
What type of virus is influenza?
RNA virus - Orthomyxoviridae
A, B, C
Which influenza groups affect humans?
IfB
IfC
Which influenza surface proteins affect humans?
Haemagglutinin (H) 18 types
Neuraminidase (N) 11 types
What is the role of Haemagglutinin?
Facilitates viral attachment and host cell entry
What is the role of Neuraminidase?
Enables new virion to be released from the host cell
What is antigenic drift?
Small, on-going point mutations in the genes coding for antibody binding-sites
What is the effect of antigenic drift?
Change the antigenic properties, so immune system cant combat it
(reduces immunity/vaccine effectiveness)
What is antigenic shift?
Abrupt change in virus - new H/N combinations
2 or more strains combine to form new subtype
What is the effect of antigenic shift?
Jumping from species - species
Can combine to form
Reassortment of virus gene segments
Can lead to pandemics
What virus was implicated in the 2009/10 pandemic?
H1N1
How does pandemic flu differ from seasonal flu?
Pandemic:
Sporadic
25%+ population
More serious
Seasonal:
Every winter
10-15% population
Unpleasant
What are the requires for a pandemic?
Human pathogenicity
Antigenic shift = susceptible population
Efficient person-person transmission
Which Avian flu strains effect humans?
H5N1
H7N9
How is Avian flu spread?
Direct contact with infected birds
Human-human
What is the fatality rate of Avian flu?
H5N1 - 60%
H7N9 - 36%
Where is avian flu still present?
H5N1 - Egypt
H7N9 - China
What are the clinical features of influenza?
2-4 day incubation Abrupt 41C fever 3 days 2 or more of: Cough Sore throat Myalgia Headache Malaise
What is Influenza-like illness?
Fever >38C AND
Cough
Onset within last days
How is influenza transmitted?
Airborne - droplets >5um
Contact
What is virus shedding?
First 4 days of illness
longer in children/immunocompromised
How long is virus survival?
24-48hrs on non-porous surfaces
8-12hrs on porous surfaces
What are the risk factors for complicated influenza?
Neurological, hepatic, renal, pulmonary and chronic cardiac disease
Diabetes mellitus
Severe immunosuppression
Age over 65 years
Pregnancy (+ up to two weeks post partum)
Children under 6 months of age
Morbid obesity (BMI ≥40)
What are the common complications of influenza?
Acute Bronchitis
Secondary bacterial pneumonia
How does Secondary bacterial pneumonia present?
4-5 days post-flu
S. pneumoniae
Staph aureus
H. influenzae
What are the less common respiratory complications of influenza?
Primary viral pneumonia
What are the less common cardiac complications of influenza?
Myocarditis/pericarditis
What are the less common CNS complications of influenza?
Transverse myelitis/Guillain-Barre
Myositis & Myoglobulinaemia
How does primary viral pneumonia present?
Common in H5N1
Rapid respiratory failure (48hrs)
Mortality >40%
What is encephalitis lethargica?
Post-influenza sequelae
How does encephalitis lethargica present?
Fever Headache External ophthalmoplegia Lethargy Sleep reversal Postencephalitic Parkinsonism 25% mortality
How is influenza diagnosed?
Viral nose/throat swabs PCR Chest x-ray (pneumonitis/ia) Blood culture Pulse oximetry Respiratory rate U+E, FBC, CRP
What is the function of CRP monitoring in influenza?
Monitoring pneumonia recovery
CRP should halve in 4 days
When is an urgent CXR indicated in pneumonia?
Flu like symptoms and fever for >4 days
Which severity assessment is used for pneumonia?
CURB-65
What does CURB65 stand for?
Confusion Urea (>7mmol/l) Resp rate (>30) Blood pressure (<90sys, <60dia) >65y/o
Which medications are used for influenza?
Neuraminidase Inhibitors (antivirals)
Within 48hrs
Oseltamivir (Tamiflu)
Zanamivir (Relenza)
Which medications are used for influenza? (Hard)
Neuraminidase Inhibitors within 48hrs Oseltamivir (Tamiflu) Dose - 75mg every 12hrs 5 days Zanamivir (Relenza) Dose - 10mg inhaled daily up to 10 days
What side effects are associated with Oseltamivir?
Nausea + Vomiting Abdominal pain Diarrhoea Headache Caution in renal failure
How is complicated influenza managed?
Oseltamivir (oral)
Zanamivir if resistant/poor response
What are the less commonly used antivirals in influenza?
Peramivir - IV (uncomplicated)
Flavipiravir - oral
Baloxavir Marboxil
How is antiviral therapy managed in pregnancy?
Oseltamivir
How is antiviral therapy managed in breastfeeding?
Oral Oseltamivir
When does an individual become non-infectious?
24hrs after last symptoms
or
When anti-viral therapy is completed
(in immunocompetent adult)
How can healthcare staff protect themselves from flu in patients on nebuliser/NIV?
Face fit respirator mask
