Influenza Flashcards
Where does the name influenza come from?
‘influentia’ – meaning influence of the stars
When does seasonal influenza occur?
Dec – Feb in the Northern Hemisphere Jun – Aug in the Southern Hemisphere
How often does more severe episodes of influenza occur?
More severe epidemics of influenza occur every 11 years
What is a pandemic?
When the virus spreads across the whole globe
What was the most severe outbreak of influenza?
1918-9 ‘Spanish Flu’
When was the most recent severe pandemic?
2009/10 - Swine Flu
What are the three main types of influenza and who do they affect?
A (1933) - affects mammals and birds B (1939) - humans C (1950) - humans
What is the role of surface proteins?
Surface proteins is what meds target and what creates a new strain of virus
What is the H antigen and action?
Haemagglutinin (H) - facilitates viral attachment and entry to host cell
What is the N antigen and action?
Neuraminidase (N) - enables new virion to be released from host cell
Which H antigens label a human virus?
H1 - 3
What is antigenic drift?
- Mechanism of variation within the virus. - Occurs continually over time, small on-going point mutations in the genes coding for antibody binding-sites
What are the implications of drift?
Change the antigenic properties and eventually the immune system will not combat the virus as well Causes worse than normal epidemics & vaccine mismatch [every year WHO try to match these mutant viruses attempting to create vaccines]
What is antigenic shift?
Abrupt major change in the virus, resulting in new H/N combinations - process by which two or more different strains of a virus combine to form a new subtype, resulting in new H/N combinations
What are the implications of shift?
The genetic change that enables a flu strain to jump from one animal species to another
How quickly can a influenza virus spread?
3 days to spread from 4 countries to worldwide
What is the differences between seasonal flu and pandemic flu?
Seasonal flu: - every winter - 10-15% of population - unpleasant but not life threatening Pandemic flu: - occurs sporadically - affects 25% of population - more serious, can be life threatening
What are requirements for the occurrence of a pandemic?
- human pathogenicity - ‘new’ virus (antigenic shift) - Efficient person-person transmission
What is the wave phenomenon of pandemics?
it occurs sporadically (on a graph looks like a wave)
What is notable about the age of mortality in pandemics versus seasonal flu?
- seasonal flu effects young and old most severely - pandemic flu effects the middle age group more severely
How does avian flu spread?
Spreads through direct contact with infected birds, dead or alive
What is the fatality rate of avian flu?
High case fatality rate: 60% (H5N1), 36% (H7N9)
What is the incubation period of infuenza?
2-4 days
What is the most common presentation? What are the main additional features?
*abrupt fever up to 41 degrees lasting up to 3 days* + 2 or more of: cough, sore throat, myalgia, headache, malaise
