Influenza Flashcards
What are the main characteristics of the influenza viruses?
1-Single stranded RNA virus
2-Negative sense
3-Enveloped-spikes/proteins within envelope.
4-Segmented genome
5-seasonal influenza: Causes epidemics on a yearly basis during the winter. Why? Closed inside vs melatonin and immune system
What are the proteins found on the surface of the influenza viruses? Why are these important ?
Hemaglutinin: sticks the viruses to the cell receptor. This is the protein used in vaccines. Antibodies bind to this protein
Neuraminidase: frees the virus to infect other cells. Can get past the mucous layer and into the cell because of this protein
This is how we subtype the virus: H1N1
What are the three influenza viruses?
A: has the greatest pandemic potential. Usually more severe
B:
C: not important
What is antigenic drift?
- Occurs in influenza A and B
- Contribute to epidemics and is the reason why the seasonal flu shot changes each year
- always mutating because of sloppy polymerase
- Darwinian evolution:best mutation survives
What are the clinical conditions of the upper respiratory tract caused by viral infection ?
Rhinitis
Pharyngitis
Laryngitis
Most people have viral infections localized to upper respiratory tract
The vocal cords separate upper and lower
What are the clinical conditions in the lower respiratory tract caused by viral infection ?
Tracheitis
Bronchitis
Bronchiolitis
Bronchopneumonia
How is influenza spread?
respiratory droplets: we need to breath it in because our salicylic acid receptors are in our RT.
Soiled hands
What is antigenic shift and why is it important?
- larger changes than antigenic drift
- virus takes advantage of segmented genome
- not predictable
- pandemics
- two different influenza viruses(Avian and human )infect the same cell (pigs) and then genes are swapped creating a whole new virus
Why are pigs important in context of influenza pandemics?
Pigs have receptors in their respiratory tract for avian and human strains of virus. Genes swap and new virus is created and spread
Humans can however, get avian virus directly from avian host
What are the three components needed for a pandemic to occur?
1-requires a completely novel virus. No immunity
2-easily infects human
3-easily transmitted
How are respiratory viruses including influenza spread?
1-droplet spread( fast majority are not airborne)
2-contaminated hands
3-fomites/objects
4-aerosol is controversial
Describe the mechanism of influenza infection?
1-inhalation of droplets
2-attachment to Salic acid on upper respiratory mucosa
3-primary replication
4-can migrate to the lungs after primary replication. Bad disease. Can cause pneumonia. Cytokines cause inflammation which leads to collateral damage to surrounding cells. Kills cells to prevent spreading.
5-cytokines release/storm(storm is worse in adults)
6-problems with muscles(aches), cardiac depression,other organs
What are the main clinical characteristics of the influenza infection?
1-fatigue for a long time. Even after infection
2-fever
3-cough
4-headache
5-muscle pain
Flu predisposes you to bacterial infections because it stripes sialic acid from RT leaving receptors for bacteria. leaves you vulnerable to pneumonia( pneumococcus,s.aerus,strep)
What are the three main categories of complications of influenza? What diseases are in each category ?
1- lower respiratory tract complications including croup and bronchiolitis in kids as well as primary influenza pneumonia
2-secondary bacterial infection including pneumonia and otitis media
3-other complications such As heart failure
Who are at higher risks for complications from the influenza virus ?
During the last pandemic, what other risk factors did we discover?
1-the elderly, esp those in care units/homes
2- patients with asthma, CF, heart disease, immunosuppression, haematological disorders, renal failure, diabetes
Last pandemic: pregnancy( immunosuppression, pressure on diaphragm) aboriginal populations(isolation, genetics), morbid obesity, current smokers
