How the coronavirus (COVID-19) actually works inside the body and why it’s so deadly

Explaining science of how deadly virus works

DETROIT – Perhaps it’s the fear of the unknown and the solace of an answer, or maybe it’s just curiosity, but since the beginning of the coronavirus (COVID-19) outbreak, many viewers have asked how the virus actually kills people.

UPDATE -- April 2, 2020: Michigan coronavirus cases up to 10,791; Death toll now at 417

“I’m going to purposely keep this explanation fairly basic," Dr. Frank McGeorge said. “Also, please understand: In the vast majority of people, the illness doesn’t progress to the end stage that I’m going to describe here.”

Early stages and mild cases

Starting from the beginning, the virus attaches to cells that cover your mucosa, which is the lining of your eyes, nose, mouth and throat.

Once the virus gets in the cells, it sets up shop and hijacks them to make more virus, which then spreads to other adjacent cells.

This is just the way all viruses work, and other coronaviruses, such as the ones that produce the common cold, stop in the nose or throat, and that’s why all you feel is a runny nose or sore throat.

In fact, that’s where the story often ends even for people with COVID-19. Your body successfully defends itself, and all you have is a mild illness.

Deadly cases

Unfortunately, SARS-CoV-2, the COVID-19 virus, is different than other coronaviruses. In at least 20% of people, it has a tendency to move lower in the respiratory tract.

When it gets into the trachea, bronchi and lungs, that’s where the problems start.

If the virus doesn’t make it deep into your lungs, but just causes irritation, you get the dry cough that many people have described. The illness stops here in many people.

But if the virus does make it into your lungs, it hijacks and kills cells there to reproduce.

Questions about the coronavirus (COVID-19)? Ask Dr. McGeorge

All this time your body is fighting back, but that fight causes a lot of damage and inflammation, leading to pneumonia and even worse -- acute respiratory distress syndrome (ARDS), which is when the lungs stiffen and fill with fluid.

Pneumonia -- infection-related lung damage -- is what causes people to feel a worse cough or shortness of breath as the the lung damage prevents them from absorbing oxygen.

Pneumonia and ARDS ultimately lead to respiratory failure, and that’s when people need breathing tubes and ventilators. The machines breath for you with higher concentrations of oxygen and extra pressure to overcome the stiffening and fluid buildup.

People can die when they simply cannot overcome the lung damage, even with a ventilator.

Causes of other symptoms

What about some of the other symptoms, such as fever or body aches?

Those symptoms come from your own body as your immune system fights and releases special proteins called cytokines. In some cases, the level of the cytokines can get high enough that they cause collateral damage in other organs.

The heart, in particular, is heavily involved in the fight, and early signs of heart damage are also associated with a worse outcome.

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The bottom line is that lung injury is the main cause of death, but that lung injury is significantly worse because of the inflammation caused by our own bodies fighting against the virus.

The more unusual symptoms, such as amnesia, loss of smell or dysgeusia -- change in taste -- are likely triggered because the virus is affecting the nerves that carry those senses.

The olfactory nerve, for smell, is at ground zero for the infection, and obviously, the tongue is directly nearby.

Damage to other organs can also cause death and complications, but respiratory failure is the No. 1 reason coronavirus is so deadly.

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