17-18: SARS-CoV-2 Flashcards
what’s very impressive about SARS-CoV-2?
identified and sequenced in 5 weeks because of new technologies
COVID hospitalisation and death by age
big variations by age
higher changes of death from COVID the older you are
COVID hospitalisation and death by race/ethniciy
systemic health and social inequities
less access to healthcare and issues getting access to medication
COVID hospitalisation and death by pre-existing conditions
more likely to be severely affected if you’re elderly or have co-morbidities
e.g. asthma, hypertension, obesity, diabetes, chronic kidney disease, severe obesity, etc.
vaccines for COVID
all quite efficient
e.g. pfizer, moderna, astrazeneca, covishield, J&J, sinovac, sinopharm, etc.
time for COVID vaccine innovation
speed was astounding so fear in the population about this speed
- less than a year between virus discovery and vaccine
measles which was relatively quick still took 10 years, polio took 50 and typhoid took 100
why did we get a COVID vaccine so quickly?
coronaviruses were already a concern
- SARS-CoV-1 and MERS as spillover from bats/camels making people very sick
- knew how to grow vaccines and which proteins needed to be targeted with antibodies
technology was ready
worldwide collaboration
funding for COVID research
close collaboration between pharmaceutical companies and government agencies
high infection rates so no difficult recruiting volunteers
variants of the virus
virus invading the population, people getting infected, some resistance associated with vaccination and re-infection
many waves with virus banging to find a way to re-enter or relaunch a massive infection despite variants dying out
- slightly changes don’t change how the virus infects cells but prevents antibodies from recognising the virus so better at escaping immune responses
delta 2-4x more virulent/infectious than alpha
- recognises the cells it needs to enter more efficiently
- mutations on the spike which make it better at recognising/interacting with cells
omicron generally 2.4-3.2x more transmissible than delta in vaccinated household contacts
- no difference in unvaccinated
what types of antibodies are produced with the vaccine?
need two doses
with the first dose, you don’t have that many antibodies but you do make more IgM (lower affinity antibodies that don’t improve with time) and very few IgG
durability of vaccine-induced antibodies against SARS-CoV-2
benefit of the vaccine wane, at least for antibodies and not necessarily T-cells
need for a booster, whether or not you are infected naturally
- probably never done with SARS-CoV-2 since the variant is able to escape and there is waning immunity
initial COVID infection
virus finds ACE2 receptors in the lining of the nose
- proteins recognised by the virus’ spike proteins
virus enters, makes myriad copies of itself, invades new cells
- transmission through droplets when you cough, breathe and even if you’re asymptomatic
symptoms can be absent or you develop a fever, dry cough, sore throat, loss of smell/taste, head/body aches
COVID infection in the lungs
after entering through the nose, virus goes down the windpipe to attack lungs
- this is where it can turn deadly
tiny air sacs called alveoli at the end of the lung’s respiratory tree which are lined with cells rich in ACE2 receptors
- alveoli have a lot of surface area for infection
what normally happens in the alveoli?
oxygen crosses alveoli into capillaries (tiny blood vessels beside the air sacs) and it is carried o the rest of the body
exchange of O2 and CO2
pneumonia associated with COVID
virus replicates in alveoli
- inflammation of alveoli so immune cells recruited to kill cells
- dying cells release cytokines, immune cells release cytokines and chemokines
leaves behind fluid and dead cells/pus behind
- increased fluid uptake in the lungs
- reduced ability of the blood to contain oxygen since blood comes back with fluid
underlying pathology of pneumonia with cough, fever and rapid/shallow respiration
acute respiratory distress syndrome (ARDS)
deterioration from pneumonia to develop this condition
- plummeting oxygen levels with a hard time breathing
- need ICU and artificial oxygenation
autopsies show alveoli are stuffed with fluid, white blood cells/immune cells, mucus and detritus of destroyed lung cells
- not a disease of the virus
- disease of the immune system which reacts very strong to eliminate the virus (hyper-activation)
cytokine storm
- too many cytokines which create too many immune cells and proteins
- immune system too stimulated
