Knowns and unknowns about coronavirus

Knowns and unknowns about coronavirus

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


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


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