Lecture 7 Influenza Flashcards
What is the structure of the influenza virus
RNA virus
8 segment genome
What are the 3 main groups?
A- infects mammals and birds
B and C only humans
What is the function of surface protein haemagglutinin
Facilitates viral attachment and entry to host cell
what is the function of the surface protein Neuraminidase
Enables new virion to be released from host cell
What is Antigenic Drift
Mechanism of genetic variation within the virus
Occurs continually over time, small on-going point mutations in the genes coding for antibody binding-sites
Can cause worse than normal epidemics and vaccine mismatch
What id Antigenic Shift
Abrupt major change in the virus, resulting in new H/N combinations
The process by which two or more different strains of a virus combine to form a new subtype, resulting in new H/N combinations can lead to pandemics
Name 3 pandemic requirements
Human pathogenicity
Antigenic shift (new virus)
Efficient person-person transmission
Clinical features of influenza
Incubation period 2-4 days (range 1-7 days)
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
WHO definition if influenza like illness
Fever (>38°C) and
Cough
Onset within the last 10 days
High risk groups
a. 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)
What are common respiratory complications
Acute bronchitis
Secondary bacterial pneumonia
What are less common complications
Primary viral pneumonia
Myocarditis/pericarditis
Transverse myelitis/ Guillain-Barre
Myositis & Myoglobinuria
Diagnosis and Investigations for influenza
Viral nose and throat swabs- PCR CXR Blood culture Pulse oximetry Respiratory rate U&Es, FBC, CRP
What investigations are required for someone with suspected secondary bacterial pneumonia
Urgent CXR Confusion Urea >7mmol/l Respiratory rate >30mm Blood Pressure (diastolic <60 or systolic <90) >65 years of age
How is c influenza treated pharmacologically
Antiviral Therapy
