Influenza Flashcards
When does seasonal influenza occur in the northern hemisphere?
Winter months (Dec- Feb)
When are severe epidemics of influenza observed periodically?
Every 11 years
What type of virus is influenza virus?
RNA
What are the 3 main groups of influenza?
A,B,C
What type of influenza only infects humans?
B & C
What H antigens are detected in humans?
H1-3
H18
What is the name given to the mechanism of genetic variation within the virus?
Antigenic drift
What is antigenic diff?
Point mutations in the genes coding for antibody binding sites. No longer recognised by immune system
What is an antigenic shift?
An abrupt major change in the virus, resulting in new antigen
How can antigenic shift occur?
When 2 different strains of a virus combine to form a new subtype
What can lead to a pandemic?
Antigenic shift
What is the difference between seasonal flu & pandemic flu?
Ordinary outbreaks occur every year during winter months whilst pandemics can occur at any point in year and are less frequent.
What % of the population is affected by seasonal flu?
10-15%
What % of the population is affected by pandemic flu?
25% +
Which type of flu, seasonal or pandemic, is usually more serious?
Pandemic
What are the requirements for pandemic flu?
Human pathogenicity
New virus (antigenic shift)
Efficient person -to -person transmission
What strand of flu demonstrated a pandemic in 09?
H1N1
What population will usually be affected by seasonal flu?
Young & old
What population will usually be affected by pandemic flu?
Usually young healthy individual, in addition to extremes of age
How does avian flu spread?
Direct contact with infected birds, dead or alive
Close human to human cnotact
What are the main types of avian flu?
H5N1
H7N9
How long is the incubation period of flu?
2 - 4 days
What other clinical features are observed in flu?
Abrupt fever Cough Myalgia Headache Malaise Sore throat
What is the WHO definition of flu?
Fever (>38) AND
cough
Onset within last 10 days
