Influenza Flashcards
Describe the influenza virus structure and groups
- RNA virus - 8 segment genome
- Orthomyxoviridae family
- Three main groups: A, B and C
- IfA infects mammals and birds
- IfB and IfC only affects humans
What are the surface proteins found on influenza?
- 18 different H antigens and 11 different N antigens
- Haemagglutinin (H): facilitates viral attachment and entry into host cell
- Neuraminidase (N): enables new virion to be released from host cell
How is the flu strain able to jump from one animal species to another?
Antigenic shift
Describe the features of avian flu
- H5N1 and H7N9 affect humans
- Spreads through direct contact with infected birds, dead or alive
- Occasional transmission via close human contact
- High case fatality rate (60%)
What are the clinical features of flu?
- Incubation period 2-4 days
- Fever (approx. 3 days)
- Plus 2 or more of: cough, sore throat, rhinorrhoea, myalgia, headache and malaise
- Less common symptoms: nausea, vomiting and diarrhoea
What is the WHO definition of Influenza like illness?
- Fever (>38)
- Cough
- Onset within the last few days
What are the symptoms of swine flu?
- Sudden fever and cough
- Tiredness and chills
- Headache, sore throat, runny nose and sneezing
- Diarrhoea, stomach upset and loss of appetite
- Aching muscles, limb or joint pain
How long can the flu virus survive outwith an organism?
- Non-porous surfaces: 24-48 hrs
- Porous surfaces (e.g. tissue): 8-12
What are the high risk groups?
- Neurological, hepatic, renal, pulmonary and chronic cardiac disease
- Diabetes
- Severe immunosuppression
- Age > 65yrs
- Pregnancy (including 2wks post partum)
- Children < 6 months
- BMI > 40
What are the common complications of flu?
- Acute bronchitis
- Secondary bacterial pneumonia
What are the common organisms responsible for secondary bacterial pneumonia?
S. pneumoniae, S. aureus and H. influenzae
What are the less common complications of flu?
- Primary viral pneumonia
- Rapid resp. failure
- Myocarditis/pericarditis
- Transverse myelitis/Guillian-Barre
- Myositis and myoglobinuria
What investigations can be done?
- Viral nose and throat swabs
- CXR
- Blood culture
- Pulse oximetry
- RR
- U&Es, FBC and CRP
When should patients with flu have an urgent CXR?
Flu symptoms and a fever for >4 days
What is Oseltamivir (Tamiflu) and what are the potential adverse effects?
- Oral Antiviral therapy
- Common S/E: Nausea, vomiting, abdo pain and diarrhoea
- Less Common S/E: headache, hallucinations, insomnia and rash
What is Zanamivir (Relenza), how is it administered and what is the potential adverse effects?
- Antiviral therapy
- Dry powder inhaler
- Rare S/E: occasional bronchospasm
When should antivirals be used to treat influenza?
- Uncomplicated patients who are severely immunocompromised or at serious risk of developing complications
- All complicated patients
Name other antiviral medications
- Peramivir: IV
- Favipiravir: Oral
- Baloxavir Marboxil
What is the guidance for the use of antivirals during pregnancy and breastfeeding?
- Recommended in pregnancy due to adverse outcomes
- Oseltamivir is first line in both pregnancy and breastfeeding
- Zanamivir can also be used during pregnancy
When does an individual become non-infectious?
24hrs after last flu symptoms or when anti-viral therapy is completed (whichever is longer)
What protection should healthcare staff use when a patient is suspected to have flu?
- Surgical face mask
- Plastic apron
- Gloves
- Hand hygiene
- FFP3 Respirator mask if the patient is on a nebuliser, NIV etc.
Which types of flu are normally found in the flu vaccine?
2 Type A and 1 Type B subtype viruses
