W28 - Viral pandemics and influenza Flashcards
the 2 viruses responsible for pndemics in the 21st century are:
the 2 viruses responsible for pndemics in the 21st century are = SARS-CoV-2, infleunza
How many pandemic influenzas took place in the past?
4!
How many people died as a result of the 1918 Spanish flu pandemic?
50 million
The natural reservoir of influenza A virus is…
Ducks (aquatic birds)
What are the 2 spike proteins in influenza virus?
- Haemagglutinin (HA)
- Neurominidase (NA)
Why can’t avian influenza viruses infect humans too well?
Avian influenza viruses (in ducks) are not evolved to spread too well between humans and also cause too severe of a disease in humans because viruses are intracellular and so the adapt to their host usually. the identity of cellular machinary in birds will be diff to humans = this is called host gene barrier
What is an imp mutation that avian influenza needs to hve to be able to replicate/spread in humans?
mutation in PB2 subunit => changes ANP32 protein
What is antigenic shift?
Influenza virus have 8 gene RNA segments, which means if 2 strains co-infect and replicate in the same cell, you could get a mixing of genetic content = reassorted virus with new host range and replication cabalities = antigenic shift
google definition: antigenic shift, genetic alteration occurring in an infectious agent that causes a dramatic change in a protein called an antigen
Antigenic shift will lead to adapted influenza virus that has the potential to cause pandemics - T or F?
False - Antigenic shift is not sufficient for evolution of a pandemic virus.
The virus will be able to infect human/mammalian cells, but it needs to become adapted to being spread from human-to-human
Human influenza viruses transmit between people in…
airborne droplets
What limits avian influenza to transmit between humans?
Avian flu HA can bind to human receptors in deep lungs (hence cause severe disease and death, for example amongst those working in poultry markets), however it cannot bind well to receptors in the URT, so can’t spread between humans.
It needs to acquire affinity for human receptors to be able to penetrate mucus and infect epithelial cells
Describe pH & its relationship with avian influneza entry + airborne droplets
virus floats in through air, lands on receptor, endocytosed => the virus expeirences this mildly acidic environment of early and late endosome, this triggers virus to release its genome and start replicating. the HA component is pH sensitive
airborne droplets => the first droplet is mildly acidic, but as water evaporates, the concentration of ions, including H+, will increase = the pH goes LOW (ACIDIC). avian influenza viruses are very fragile in pH and they become inactivated in the air before they are picked up by next individual.
Name 3 main adaptations avian influenza needs to have to be able to infect humans
- Polymerase change
- HA change (to bind better to URT)
- Altered ability to survive low pH
Several antiviral drugs already exist for influenza, and are licensed for use in the clinic. However unlike HAART for HIV we don’t use them together. T or F?
true - they are not licensed to be used in combination
What is the MOA of neuraminidase (NA) inhibitors?
the virus uses NA to bud out of infected cells
- if patient is taking an NA inhibitor drug, that drug would be blocking the NA = the virus would be tethered to the cell surfce = halt viral replication and virion woul be picked up and killed.
