SARS-CoV-2 is the virus that causes Covid-19,
the respiratory disease that has been ravaging the world.
The virus is so tiny that it can only be viewed
through an electron microscope.
It’s about 80 to 120 nanometers in diameter,
about one thousandth of the width of an eyelash.
Scientists around the world have been studying what the virus does to our cells,
hoping to better understand it and eventually defeat it.
Here’s what we know so far.
By sequencing, people have actually discovered literally hundreds of coronaviruses,
but the main ones which affect humans are the seasonal ones,
the NL63, the HKU1, the 229E.
And then we have these three moderately severe ones,
the SARS, the MERS, and now this new one.
They're called corona because the Latin word means crown,
because when people looked at them using electron microscopy,
they found there's these little spikes, or crowns,
which surrounded the virus.
These spikes are what the virus uses to attach to cells.
So all the coronaviruses, structurally,
look very much similar.
All they're different is their makeup,
or their genetic material.
A virus, by and large, can’t replicate itself,
it needs a cell to do it.
For most viruses to get into the human body,
they need something called receptors.
The new coronavirus works the same way.
This virus uses a receptor which is called ACE2,
which represents angiotensin-converting enzyme 2.
This is a receptor which is present mainly in the respiratory tract
also the gastrointestinal tract.
And so what happens is that this spike protein,
remember that's what gives the virus its structure,
the spike protein is what binds to this ACE2 receptor.
The new coronavirus targets specific cells in our nose,
mouth, eyes, gut and intestine
where it can find ACE2 receptors to unlock the cell.
Once the virus enters, it hijacks the cell
and turns it into a virus producing factory.
It fuses its lipid membrane with the membrane of the cell
and releases its genetic material called RNA.
The infected cell reads the RNA
and begins making proteins that keep the immune system at bay
and proteins that allow the assembly of copies of the virus.
Then the newly assembled copies are carried to the outer edge of the cell
and can go on to infect other cells.
Within one square micrometer, you can get 1,600 viral particles.
So each cell can produce up to about 600,000 viral particles.
Some viruses, when they actually replicate in the cell,
they'll kill the cell,
and that is what's called a cytopathic effect,
and that can actually then lead to some of the symptoms.
But what we've found is that this virus is not very toxic,
or it doesn't cause that much of a cytopathic effect for a long period.
In influenza, it can start killing the cell within a couple of days.
But this virus seems to not kill a cell for about five to six days.
And this means that the patient may then be having vast replication,
but because it's not killing the cell,
there can be very few clinical symptoms,
and that's why it's been found what's called the asymptomatic carriers.
But as the infection progresses,
many patients develop typical flu symptoms
like fever, dry cough and tiredness,
As well as atypical symptoms like a loss of smell and taste,
This is the immune system fighting to clear the virus.
When an infected person coughs or sneezes,
virus-containing droplets can be emitted on nearby people and surfaces.
The coronavirus can survive on different surfaces for several hours to several days.
But it’s vulnerable and easy to kill.
So many of the common alcohols and bleaches,
they can alter the PH and alter the surface
or the outsides of this virus,
which is basically able to disrupt the envelope,
therefore not making it infectious.
And then there's the environment.
So studies which have been done by colleagues in our institution
show that this virus is actually temperature sensitive.
So at four degrees Celsius
the virus can remain very stable for a very long period of time.
At 25 degrees Celsius it remains stable for about five days.
At 35 degrees, stable for one to two days,
and at 56 degrees, for about maybe 30 minutes.
So the warmer the environment, the less stable it is.
Currently, there is no effective treatment for the virus.
Recovery depends on if the immune system can develop antibodies
to recognize the virus’s structure
and then destroy the virus,
helping fight off the disease.
That's why people talk about herd immunity,
is that once you get enough of the population
which has been exposed to the virus
and which has the antibodies,
that will then decrease the spread of the virus from person to person.
So that's why some people think that we'll have to wait
until we get enough people becoming infected
that we get the herd immunity.
But that's going to take a long, long period of time.
So the alternative is to then bring in these vaccinations,
so that if you can vaccinate people,
then you can basically build up, hopefully,
enough immunity to stop the transmission from person to person.
Developing a vaccine that proves safe and effective
may take a year or more.
Medications to fight the disease may be available sooner,
but there is no quick fix to arrest the pandemic.
So the only way for potentially getting this virus under control,
is going to be the social ways,
social mechanism,
which is social distancing, quarantining,
and basically a rigid attention to personal hygiene
and to the environmental hygiene.
Many people who have been infected with Covid-19 have recovered.
Some governments suggested that people who have antibodies to the coronavirus
could be issued an “immunity passport”
that would allow them to travel or return to work.
But the World Health Organization said
catching Covid-19 once may not protect you from getting it again.
The use of such “immunity passports”
may increase the risks of continued transmission.