Influenza Flashcards
What is the INFLUENZA VIRUS structure
RNA virus. 8 segment genome
IfA infects mammals and birds, IfB & IfC only …
Humans
Haemagglutinin (H) allows
viral attachment and entry to host cell
Neuraminidase (N) allows
new virion to be released from host cell
ANTIGENIC DRIFT
Mechanism of genetic variation within the virus
pandemics flu occur
three times each century and can arise at any time of the year
PANDEMIC REQUIREMENTS (3)
Human pathogenicity
‘New’ virus (antigenic shift)
- susceptible population
Efficient person-person
transmission
AVIAN FLU - features
Spreads through direct contact with infected birds, dead or alive
- COULD SPREAD via close human contact
Clinical features of influenza (4)
Abrupt fever up to 41°C (commonly 38-40°C) which lasts 3 days (range 1-5 days)
Plus 2 or more of: Cough, [sore throat, rhinorrhoea], myalgia, headache, malaise.
Predominance of systemic symptoms
Less common symptoms: Nausea, vomiting, diarrhoea
-
if requires hospitalization defined as ?
severe acute respiratory infection (SARI)
Symptoms of swine flu
sudden fever nd sudden cough
tiredness, chills, headache, sneezing, diarrhoea, aching muscles
Transmission of swine flu
Airborne – person person by large droplets >5 microns
Contact – direct (person person)
– indirect (person fomite person)
Virus shedding occurs
First 4 days of illness (range 1-7 days)
Longer in young children & immunocompromised
Virus survival occurs
24-48 hours on non-porous surfaces
8-12 hours on porous surface e.g. tissue
HIGH RISK GROUPS - risk factors for complicated influenza
Neurological, hepatic, renal, pulmonary and chronic cardiac disease
b. Diabetes mellitus
c. Severe immunosuppression
d. Age over 65 years
e. Pregnancy (including up to two weeks post partum)
f. Children under 6 months of age
g. Morbid obesity (BMI ≥40)
Common respiratory complications
Acute Bronchitis
Secondary Bacterial Pneumonia (~20%)
Appears 4-5 days after start of ‘flu
Organisms seen in microbiology for common respiratory complications
H.influenza, S.pneumoniae, βhaem.strept
Staph.aureus (>2/3rds)
Less Common Complications, respiratory, cardiac and CNS
Primary viral pneumonia
Myocarditis/pericarditis
Transverse myelitis/Guillain-Barre
Myositis & Myoglobinuria
ENCEPHALITIS LETHARGICA
Fever, headache
External ophthalmoplegia
Lethargy
Sleep reversal
DIAGNOSIS & INVESTIGATIONS - (6)
Viral nose and throat swabs/VTS (Molecular detection /PCR; using flocked swabs)
Chest X-ray – pneumonitis/pneumonia/ARDS
Blood culture
Pulse oximetry – SpO2 <92% need ABG and oxygen
Respiratory rate !
U & E’s, FBC, CRP (CRP monitoring recovery of pneumonia - should halve in 4 days)
SECONDARY BACTERIAL PNEUMONIA
Patients with ‘flu symptoms and a fever for > 4days – should have an urgent CXR
The severity assessment
C(U)RB-65 score Confusion Urea >7mmol/l Respiratory rate >30mm Blood Pressure (diastolic <60 or systolic <90) >65 years of age
What should you use ASAP
ANTIVIRAL THERAPY
ZANAMIVIR (RELENZA) – Inhaled & or I.V.
OSELTAMVIR
Other antiviral therapy
Peramivir (Alpivab®) - IV
Favipiravir (Avigan) - ORAL
Baloxavir Marboxil - one dose
Amantadine & Rimantadine
When does an individual become non-infectious
UNOCOMPETENT ADULTS
24hrs after last flu symptoms (fever & cough)
Or when anti-viral therapy completed
Which ever is longer
vaccination?
Seasonal flu vaccine
