B2 High-Intermediate US 1025 Folder Collection
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- All viruses carry
some kind of genetic material, DNA or RNA.
COVID-19's genetic material is RNA
encased by a protective shell called a capsid.
This is all surrounded by an envelope made of lipids
which are essentially fats and proteins.
Spike proteins protrude out of the virus.
The RNA has all the instructions
for how this virus needs to replicate
if it had the proper machinery,
but it lacks this machinery to replicate
so it has to infect a cell.
Once the virus enters your body,
it looks for cells with the right receptors.
Specific spike proteins
bind to a specific type of receptor called ACE2
which stands for angiotensin-converting enzyme 2.
When the virus binds to this receptor on a cell,
it's then able to enter and release its RNA into the cell.
The cell has its own replication machinery like a ribosome
for making its own RNA into protein.
But now, the virus can hijack the cell's ribosome
and turn its own viral RNA into protein
that makes up the components necessary for a new virus.
Essentially, it turns the cell into a virus-making machine
and in the process destroys the cell.
Once it makes a ton of virus,
it breaks out of the cell destroying the cell
and all the new viruses will move on to other cells
to repeat the process.
So how does infection lead to the common symptoms
of fever, cough, and difficult in breathing?
ACE2 is found especially on cells
that line the upper respiratory tract
called goblet cells and ciliated cells.
These cells are the front-line defenders.
Goblet cells produce mucus
which traps bacteria and pathogens.
Ciliated cells then sweep the debris and mucus out
clearing away the unwanted particles.
When the virus attacks goblet and ciliated cells,
this causes inflammation and irritation in the airways
that will stimulate dry coughs.
If you're healthy, chances are your immune system
will be able to eventually fight off the infection here
before it's able to spread down
to the lower respiratory tract.
But if your immune system can't stop it
in the upper respiratory tract,
the virus will travel down to invade the lungs
and specifically to alveoli.
Alveoli are air sacs in the lungs
where gas exchange between O2, oxygen,
and CO2, carbon dioxide, occur.
The virus attacks the cells in the alveoli
and when the body detects the virus,
it signals an immune response that go into overdrive.
Immune cells are sent to the alveoli
which cause them swell and fill with fluid.
The overactive immune response
can damage more alveolar cells
causing more cells to die and slough off
filling the lungs with more debris and fluid.
This interrupts the proper transfer of oxygen
into the bloodstream
and causes alveoli to eventually collapse.
This is why difficulty in breathing
is one of the symptoms of COVID-19 infection.
Additionally, specific proteins are released
as an immune response into the blood
where they travel up to the brain
to a region called the hypothalamus.
One of the things the hypothalamus regulates is temperature.
The protein signals your hypothalamus
to increase body temperature leading to fever.
Less oxygen in your blood may mean your vital organs
don't have enough oxygen to keep working.
This can lead to organ failure causing them to shut down.
Respiratory viruses like COVID-19
are spread by respiratory droplets
that are released when someone coughs or sneezes.
These droplets can stay aloft for six feet
so they can easily be transmitted
to somebody standing nearby breathing in those droplets
or the droplets can land on surfaces
and survive on surfaces for around 24 hours.
The virus can then be transmitted by touching those surfaces
and then touching your nose, eyes, or mouth.
The incubation period is the time of infection
to appearance of symptoms
and it can be anywhere from two to 14 days.
This means you could be infected and show no symptoms.
But if you're not social distancing,
you will go on to infect others
without even knowing you're sick yet.
Soap may seem too simple to work against such a tough virus
but it actually does.
Soap has molecules that have a hydrophilic head,
meaning it's attracted to water,
and a hydrophobic tail that's repelled by water
and attracted to oil.
When you mix soap and water,
the hydrophobic parts are attracted to the oil particle
you're trying to wash off.
They stick to the oil particle
and when you rinse with water,
the hydrophilic parts follow the water
taking along with it the oily substance.
Remember that viruses have an outer envelope
that consist of lipids which act like oils.
Soap breaks apart the virus and gets it off your hands.
But it takes 20 seconds for this to completely work.
So far, testing is done by collecting samples from patients
using nasal swabs.
RNA is extracted from that nasal swab sample.
Since RNA is the genetic information of the virus,
it can be used to identify the virus
just like how our DNA is unique to identifying us.
Once the RNA is extracted,
scientists add an enzyme called reverse transcriptase
to turn the RNA into DNA.
Next, they use a polymerase chain reaction, or PCR,
to make more copies of the DNA.
To do this, scientists add primers
which are short sequences that can be designed
to attach only to fragments
that make the sample DNA uniquely COVID-19.
Fluorescent dyes are added in the mix
and fluorescence will correspond
to how much of that identifying fragment
is preset in the sample.
Thus, the amount of fluorescence
tells us the amount of virus in that sample.
If there's no virus, you'll get virtually no fluorescence.
While vaccines and potential treatments
are still being developed,
those infected may need supportive care in severe cases.
Supportive care means using ventilators
to help patients breathe and treating complications
resulting from a distracted weakened immune system.
But there's only so many ventilators
and hospital beds available.
If everyone gets sick at the same time,
we won't have enough resources, hospital beds,
doctors and nurses able to help everyone who needs it.
This is why spreading out the rate of infection
is so critical to allowing our healthcare system
to not become oversaturated.
This is why you've probably heard
that flattening the curve is so important.
That curve refers to the huge influx of cases
we're seeing without preventative measures being followed
like quarantining and social distancing.
If everyone gets sick in a short period of time,
this quickly over saturates the healthcare system,
meaning we won't have enough resources
to save the lives of those who can die from this infection.
But if everyone stays home,
we can delay the number of cases over time
and help keep the healthcare system from over saturating
so we can help as many people as possible.
How do epidemiologists describe how contagious a disease is?
For example, if one existing infection
will cause one more new infection and so on,
this would be an R-naught of one.
If an R-naught is over two,
that means every one infection
can cause two more infections.
So why is COVID-19 such a big deal?
For comparison, the average R-naught of the seasonal flu
is around 1.3.
The R-naught of the devastating 1918 Spanish flu was 1.8.
The R-naught of COVID-19 is estimated to be 2.2.
Even if we round down to two,
you can see how quickly just one infected person
can spread the virus to tons of people.
But if just one person
takes their social responsibility seriously and stays home,
look how much spread they can prevent.
This is why everyone needs to follow the CDC guidelines
and stay home so we can delay the number of cases.
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Covid-19: An Illustrated Scientific Summary

1025 Folder Collection
致平馬 published on April 8, 2020
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