Influenza virus Flashcards
List the types of Influenza virus and identify the species associated with each type.
Type A- causes flu in Humans and many other –responsible for epidemics and pandemics (pandemic world wide)→ the one we will focus on
Type B- causes flu in humans- epidemics Type C- causes flu in humans- mild disease
what is the visual difference between the seasonal influenza virus graph and the influenza pandemic of 1918 graph? (in regard to the x axis)
The season virus was U shaped higher incidence of illness related death with the very young and very old.
The pandemic virus of 1918 was W shaped (affecting the very young, very old and young adults)
explain Transmission of influenza: 3 major ways and details about each
1) Aerosol transmission- fine particles (just in normal breathing)
2) Large Droplet spray (talking, coughing)
3) Contact – direct or indirect
(unsure which mode of the 3 is most effective)
Symptoms of Influenza?
Sudden onset Fever (often high fever) Sore throat Myalgia Fatigue Cough (generally dry) Ha (abbreviation for headache) (Generally no runny nose with flu)
Identify risk groups/complications associated with influenza virus infections
Risk: children under 2 yrs old • Adults over 65 yrs old (both due to weakened immune system) • Pregnant women (for reasons unknown) • People with preexisting conditions (ie..asthma, chronic lung disease, immune compromised, heart disease)
Mortality rate: < 0.1% , however a lot of people get the flu and not always recorded
On average in the US about 23,000 deaths/yr (but varies every year from 6-48K)
Describe how climate change may affect influenza transmission?
Influenza has seasonality
Temperate climates- winter
In tropical climates- all year round→ but increase during rainy season
In sub-tropical climates- can have 2 flu seasons (winter and summer)
No one knows for certain but speculation is that climate change will bring about more opportunity for influenza.
Identify the surface molecules associated with all influenza A virus infections?
These surface molecules:
Hemoglutinin- (HA, or H)→ binds to the receptor on the cell , also responsible for virus entry- one of the major antigenic proteins (it makes an immune response )
In nature there are 16 HA’s
Called H1 – H16
Neuraminidase – (NA, or N) → responsible for the release of infected virus cells, another antigenic protein (not as important as HA)
In nature there are 9 NA’s
Called N1-N9
Commonly known: H1N1 (swine virus), H3N2 (immerged in 1968), H7N9 (immerging in China currently in humans)
Where in nature do we find influenza?
Humans Pigs Chickens Turkeys Cats (including Tigers) Horses Dogs Ferrets/mink Seals/whales Ducks/geese/waterfowl *** CENTRAL (cicle some interconnected)
- In Waterfowl ALL 16 HA’s and ALL 9 NA’s
- GI infection in Waterfowl
- Little disease in waterfowl → suggestive of it being around in waterfowl for a long time allowing it to adapt.
In humans seasonal epidemics are due to ______?
Antigenic drift
What is Antigenic Drift?
minor frequent changes in the amino acid sequence of proteins recognized by the immune system as a result of point mutations. Responsible for Epidemics (continual process) high mutation rate.
In humans Pandemics occur due to ______?
Antigenic Shift
What is Antigenic Shift?
Large, rare changes in the amino acid sequence of proteins recognized by the immune system as a result of genetic reassortment. (global change)→ responsible for Pandemics
Reassortment- is the exchange of portions of RNA between influenza viruses.
How is Reassortment possible for influenza virus?
reassortment is possible because influenza has a SEGMENTED GENOME ( 8 separate segments)
So if 2 viruses combine it can produce and offspring with an assortment of the 16 possible segments into 8 new segments
Example: if H1N1 + H3N2 = H1N2 (and if it replicates well than you could experience antigenic shift)
Earliest documented influenza pandemic?
1500’s –> early 1800’s (but not very good data)
1st documented influenza PANDEMIC with MEDIA publicity?
1889 Russian Flu
List the characteristics of the 1918 influenza pandemic?
• 1918→ Spanish Flu- H1N1 virus- avian like virus (jumped from birds to humans directly—but not 100% sure) → origin is unclear→ earliest reports of disease came from Kansas. Occurred during WWI (probable exacerbated disease- lots of people in small areas , training camps. And international travel. Unique to this pandemic: graph was not U shaped but W shaped.
o Single most deadly outbreak of the human disease (occurred w/I a year)
o Mortality in 1918 was 2.5%
o Estimates for death was approximately 50 million (estimates vary from 20 million to 100 million)
Identify the subtypes that caused each of the pandemics beginning with the one in 1918?
(Don’t need to know dates but MUST know the correct ORDER in which they occurred )
All decendents of the 1918 virus:
o 1957→ Asian flu (H2N2)
o 1968→ Hong Kong Flu (H3N2)
o 1977→ Russian Flu (H1N1)
o 2009→ Swine Origin Flu, Pandemic H1N1, A/H1N1 (H1N1)
( the H1N1 were different not the same virus for Russian, Hong Kong, swine)
Identify the know major avian influenza virus threats to public health
Avian Influenza Virus: aka bird flu → H5N1 virus
o caused a total of 637 KNOWN infections
o most occur in SE Asia
o mortality rate (about 60%)
o however it doesn’t seem to transmit among people- little if any transmission among people (person to person)
• H7N9→ Avian virus→caused infections in people between March and June 2013
o China
o About 140 infections
o About 45 deaths
