Microbiology 19 - Influenza and Covid-19 Flashcards
What drives zoonosis of influenza viruses from wild water fowl?
Antigenic drift
What must a mutation change to produce a pandemic-producing virus ?
Transmissibility between humans
Antigenic novelty
What is the mechanism of action of amantidine, and what is it used for?
Targets M2 ion channel
Used to treat strains types of influenza virus
3 drug classes against influenza
- Amantidine
- Neuraminidase inhibitor
- Polymerase inhibitor
What class of drug is oseltamivir?
Neuraminidase inhibitor
Neuraminidase is the enzyme (spike protein) that cleaves sialic acid to allow virus to exit the cell and infect other cells
What influenza vaccines are used in the UK?
- Inactivated vaccine
- Haemaglutinnin and neuraminidase proteins
- used in adults - Live attenuated (used as a nasal spray)
- used in children ONLY
not effective in adults because they’ve encountered the viral flu antigen before
What is the most important reason why SARS 2003 was so much easier to contain than SARS Covid 19?
Patients had easily-identifiable symptoms that developed quickly and so could be isolated - covid-19 is much more insidious!
Most likely origin of COVID-19
What is a likely secondary host?
Horseshoe bats
Likely secondary host: pangolins
Describe the genome of SARS-Cov2
Huge single-stranded RNA genome
How does covid bind to cells to gain entry?
They use their spike protein to bind to ACE2 receptor in the host
How long after infection is covid infectious?
3 days
From which day is COVID-19 symptomatic?
Day 5
What is the time course of covid-19 infection?
What is the predominant variant of COVID?
Omicron - current vaccine is less effective against it, but also causes less severe infection
Omicron has a large number of Spike mutations that affect antibody neutralization
Recall 2 important factors that will be at elevated serum levels in covid infection, and can be useful clinically?
IL-6
D-dimer
What benefit is remdesivir shown to have in coronavirus?
Shortens time to recovery
In which patients is dexamethosone effective at reducing coronavirus death?
In those who are receiving oxygen
*dexatheasone is used in ITU setting
Monocloncal antibodies and small molecule inhibitors for covid
Monoclonal: Regeneron, Sotrovimab
Small molecules:
1) Molnupiravir: targets polymerase, nucleoside analgue
2) Paxlovid: targets protease
Natural reservoir of influenza A virus
- wild birds like ducks, geese and **migratory waterfowl (mostly)**
- From this reservoir, the virus can cross over to other animals
- It can also end up in mammals including humans
How does influenza enter the human cell and spread?
- The virus is particularly vulnerable during the transmission phase when it is going in between people
- They attach to cells via sialic acid receptors
- They enter through endosomes
- The acidity of the endosome triggers a fusion event by which it releases its genome into the cell
- The genome then travels to the nucleus and takes over host factors to drive transcription and translation
- New viral products are produced (proteins and genome)
- They will assemble at the surface of the cell and bud off to produce hundreds of copies of the virus
2 possible outcomes when avian influenza A crosses over into humans:
1) Sometimes they can just cause a zoonoses which is a dead end:
- can cause a severe disease but does not transmit on to other human
- People exposed to the animal can get the virus
- but not as much of a Public Health issue, as it will not cause a large outbreak
2) However, if the virus undergoes various MUTATIONS it can transform from avian to human virus:
- leading to pandemic influenza
- Pandemic influenza transforms into seasonal influenza
→ undergoes antigenic drift and human adaptation
→ changing a little bit year on year (hence vaccine is updated each year)
-Therefore, all current human influenza was originally a pandemic flu
which was originally a bird virus
-It has undergone mutations to go from a virus in birds to now infecting humans
Why does influenza B, C and D not cause pandemics?
Not in animal reservoirs
Do not exist in antigenically different form to human variants
→ humans can recognise and act against them
Can you use influenza drugs in combination?
No- but this is worrying as this risks viruses developing mutations against one antiviral
