- 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.