Known and unknowns
First coronavirus, 10,000 to 300 million years ago
Seven strains infect humans
Four that cause common colds, 2 from rodents, 2 from bats
SARS-CoV, bats
MERS-CoV, bats
SARS-CoV-2, horseshoe bats
Usually an intermediary
SARS, civet cats, (abused in China)
MERS-CoV, Camels
SARS-CoV-2 Viral Origins
Shares 96% of its genetic material with a virus found in a bat in a cave in Yunnan, China
But this bat virus does not infect people
Spike proteins in SARS-CoV-2 is different and more efficient
The 4% difference = decades of evolution
Malayan pangolins, up to 92% of their genomes with the SARS-CoV-2
Need an animal that hosts a version more than 99% similar to SARS-CoV-2
Chinese studies found no animal intermediates
Why do people respond so differently?
Infection factors
Ten viral particles might be enough to get to the throat, but are likely to be cleared by mucociliary system
100 viral particles can get down to the lungs
Pneumonia of rapid onset
Two infection points combining the transmissibility of the common cold coronaviruses with the lethality of MERS-CoV and SARS-CoV
Therefore SARS-CoV-2 can shed viral particles into saliva even before symptoms start
Host factors
Human gene variants that might explain some differences
4,000 people from Italy and Spain, respiratory failure, two particular gene variants
Tuberculosis and Epstein–Barr virus, single genes.
Immunological response
How good and how long?
Neutralizing antibodies against SARS-CoV-2
IgM first 23 days
IgG up to 49 days
Longer after severe infection
?IgA
Memory T lymphocytes
Sterilizing immunity, may last for a few months
Protective immunity, much longer
Virus mutations
Mutations used to trace spread
More or less virulent or transmissible
Reinfection and vaccination
A mutation seems to have emerged around February in Europe
More infectious to cultured cells
Vaccination
200 in development worldwide
20 in clinical trials
Awaiting placebo controlled trials
Macaque monkeys suggest prevention of lung infection and pneumonia
Neutralizing antibodies generated
Vaccine could be improved over time
