What makes this novel coronavirus the scariest so far for humans
If you do not know what you are fighting, you are unlikely to know how to fight it. When it comes to the coronavirus, however, the more we get to know about the virus, the more we realise how badly the odds are stacked against us.
Viruses, to begin with, have not been easy to take on. Their invisibility gives them a wide edge even before the fight begins, which is before they enter our bodies. Covid-19, which we have been trying to scrub off our hands, clothes, paper and poly bags, is one-thousandth the width of an eyelash.
Viruses, it seems, can bide their time to attack humans with the patience of a monk. Till the time viruses do not get a human body, they are not even technically alive. They can remain in that state for eternity. In 2014, a virus frozen in permafrost for 30,000 years was still able to infect an amoeba after being revived in a laboratory. Coronavirus is far from frozen.
This coronavirus that causes Covid-19, the SARS-Cov-2, is a novel virus. There is not one thing which scientists can say with certainty about its behaviour. We do not know of the exact way in which it is entering us. Droplet infection is definitely a way. So let’s look at how it works.
Droplet infection
When an infected person sneezes or coughs, she releases droplets in the air. A person who happens to inhale these droplets becomes the next victim. The virus can also stick to surfaces and stay put, waiting for its next target. This is called a fomite-mediated transmission.
Many experts have been assigning varying periods for which the virus can survive on a surface - on cardboard for up to 24 hours, and on plastic and stainless steel for up to three days. The shocker on that front came when US public health institute Centers for Disease Control and Prevention found that the virus on surfaces of the Diamond Princess cruise ship was potent up to 17 days after passengers disembarked. So, it can’t be conclusively said as to how long Covid-19 can stay alive on surfaces.
What happens when the virus finds its way into our system?
Once in our body, the virus spreads to the back of the nasal passage and to mucous membranes in the throat. The viral particles attach themselves onto the outer walls of the host’s cells.
The genetic material that the virus has, then breaches the cell membrane of the host cell. The novel coronavirus then hijacks the cell and comes to life. The virus uses the hijacked cell to make more copies of itself.
Numerous copies are created. These copies then break out of the cell the virus attached itself to, and begin infecting other cells in the body.
It would not be unfair to say that the only purpose the virus has in mind is to make copies of itself and multiply its race.
Peter Kolchinsky, virologist and author of The Great American Drug Deal, in a Twitter thread brings out the sly nature of the virus strikingly – also scarily. He says viruses, they may not be technically alive, but are evil geniuses.
Before a cell dies, it can churn out millions of copies of the virus. Professor Hugh Montgomery, director of the Institute for Human Health and Performance at University College London, has illustrated that 10 infected people can pass on the novel coronavirus to 59,000 people.
The R-naught, which is basically the rate at which an infected person can pass on the infection for most viral infections is 1.3 to 1.4 people. This means an infected person can infect another 1.3 or 1.4 people. The R-naught for Covid-19 is three.
So what makes Covid-19 more infectious than others?
So, now we know that viruses like to multiply and for that, they need a human cell. They need to enter a human cell to produce more of their kind. The SARS-Cov-2 isn’t too good at entering cells. But it has other advantages that make it more dangerous than other viruses.
A Lancet research has shown that the novel coronavirus sneaks in by attaching itself to a protein called ACE2. ACE2 is present on the surface membrane of human cells.
So what does the ACE2 do lying on the surface of the cells? Its job is to bind to a hormone (ACE2 hormone). This combination guides the body’s stress response. The ACE2 hormone plays a role in constricting blood vessels. When blood vessels are constricted, blood pressure rises.
When the SARS-Cov-2 sneaks in, it finds that the part that creates antibodies that help identify foreign elements in the body quickly, doesn’t know what this coronavirus looks like.
SARS-Cov-2 then assumes control of the cell’s genetic reproduction tools and begins to fulfil its life’s mission – which is to create more of its kind. This relentless duplication allows the virus to burst through the cell membrane.
It is the ACE2 which could be making the virus deadlier for those suffering from diabetes or high blood pressure. Such patients are given ACE inhibitors to limit the constriction of blood vessels.
So such people have more ACE2 receptors in the body and hence the SARS-Cov-2 can multiply faster in their bodies.
What about healthy individuals?
ACE2 is found in abundance in our body otherwise too. They exist on our tongue and oesophagus, the part of the digestive tract that connects the throat to the stomach. They are also on the heart, kidney and gastrointestinal tract.
This is perhaps the reason why many patients report a loss of appetite and diarrhea if suffering from a coronavirus infection.
Most worryingly, ACE2 receptors are present on the alveoli in our lungs.
What happens to the lungs when SARS-Cov-2 reaches them?
The alveoli is the most vulnerable part of our lungs. The alveoli are responsible for the exchange of oxygen and carbon dioxide molecules to and from the bloodstream. And this is the reason why Covid-19 patients are reporting coughs and/or trouble in breathing.
The inflammation in the lungs, and their reduced efficacy, can cause them to fill with fluids, pus and dead cells, and cause an infection, leading to pneumonia.
According to The Guardian, pneumonia caused by the novel coronavirus appears to be more severe than most cases of the disease. It also affects a larger portion of the lungs.
Delayed symptoms
One person in South Korea, known as Patient 31, transmitted the virus to over 1,100 people as she went about her life. Similar cases are being reported from across the world.
It takes about five days to two weeks for symptoms to show in an infected person. All this while, the person can pass on the infection to other people without anyone knowing.
People can be asymptomatic for different reasons. One reason is that the person’s immune system is strong. The body is not completely defenceless against the virus.
Our immune system comes into action the moment we contract a new infection. Infected cells do not surrender without giving a fight to the virus. The system tries to limit the spread of the virus by eliminating infected cells. This human body, which is at war with a virus inside, is also a carrier. The person who houses this body could suffer mild infection or may show no symptom at all.
SARS and MERS, two other diseases caused by the coronavirus, made people so badly sick and so rapidly, that they couldn’t go undetected. So, while the virus wasn’t visible, it was possible to see which body was carrying the virus. The mildness with which Covid-19 is treating some of us is perhaps its biggest weapon.
Spread through body fluids
The virus has also been found in blood and stool specimens. It is, however, unclear whether it can spread through any bodily fluids.
We do not know if the coronavirus, like the Human Immunodeficiency Virus (HIV), can spread through blood transfusion or while having sex. Now, HIV didn’t spread through kissing, but this novel coronavirus could very well, since it could bind itself to the ACE2 receptors on the tongue.
Social distancing, with your mask on, so far seems to be the best remedy to avoid infection.
As more data emerges, hopefully, silver linings on tackling it will also come forth.
Also read: Covid-19: How to contain the contagion before it is too late