US, WASHINGTON (ORDO NEWS) — If some people have coronavirus with only very mild symptoms, others may die from it.
“The coronavirus infrequently penetrates so deep into the lungs, but if it does happen, you are in great danger. Even if you connect the patient to a ventilator and pump 100% of the necessary oxygen into the respiratory system, with the most severe forms of ARDS (that is, acute respiratory syndrome), it is impossible to maintain its normal level in the blood,” says Christian Wejse, Lecturer at the Institute for Public Health at Aarhus University and an expert on infectious diseases.
What happens when small particles of the virus enter the body, and how do they manage to do such harm that the patient is ill even with additional oxygen?
In this article, we will dive deeper into the cells to better learn how, step by step, a virus called SARS-CoV-2 develops.
The virus makes the cells of the body work for themselves
We have already talked about how exactly you can get infected with coronavirus, so here we will skip this stage.
Droplets of liquid with particles of the virus enter your body through your eyes, nose or mouth – and now you are already infected. Particles of the virus immediately enter the so-called epithelial cells in the respiratory tract. There they begin to command their new host cells, ordering them to produce many copies of the virus.
The task of these copies is simple. They must invade the maximum number of airway cells before the immune system detects that something is wrong.
The most important task of immunity is to prevent the particles of the virus from reaching the cells that are deep in the lungs, because it is there that the virus can cause great harm.
Finding an uninvited guest, the immune system is alarming and causes the affected cells to produce the signaling substance interferon. This protein “programs” special protective cells so that they destroy their counterparts infected with the virus. Thus, interferon prevents the virus from filling all the lungs.
This is why headache, fever and cough begin
If the immune system manages to defeat the particles of coronavirus while they are in the upper respiratory tract, the diseased person will get off with mild symptoms: temperature, dry cough and headache.
Coughing begins when the virus enters the cells of the upper respiratory tract and irritation begins, scientists say.
Some patients with coronavirus also suffer from symptoms of a cold if they inhale particles of the virus through their nose, and they remain on the mucous membranes. Others cough with phlegm, from which infected cells that are killed by immunity come out, says Christian Weiss.
“A fever begins when immunity triggers the production of interferon, because this process raises the temperature of the body,” he explains. “When the temperature jumps, the blood flow in the brain increases, and so the head hurts.”
This stage usually lasts from four to six days, and medical attention is usually not required. However, the patient should stay at home, have as little physical contact with the family as possible and pay more attention to hygiene, recommends the Department of Health.
When interferon, on the orders of immunity, kills all affected cells, the temperature will drop and the person will recover. On this, the disease will stop in most infected, studies show.
When a disease takes a serious turn
But in some patients with COVID-19, symptoms are not limited to fever, cough, and headache.
When a coronavirus infection seriously affects the body, an acute respiratory syndrome can develop, says Christian Weiss.
“This is a very, very strong pneumonia, in which so much fluid accumulates in the lung tissues that oxygen simply cannot penetrate the blood,” he explains.
The prerequisites for acute respiratory syndrome are related to the fact that the immune system either fights the virus very poorly or has not even found it in the body.
In this case, the virus particles spread freely throughout the cells and eventually reach the alveoli. These are tiny sacs located at the ends of the canals that pierce the lungs. There we get the air we breathe with oxygen.
Alveoli perform an important function, because it is thanks to them that oxygen is sent through small blood vessels to all cells of the body so that they can do their job. Cells of the body, in turn, send unnecessary waste material, carbon dioxide, back into the alveoli through the vessels. Such an exchange is called diffusion.
Immunity detects danger too late
If the particles of the virus have already managed to reach the alveoli, when the immune system finally begins to fight them, the exchange of oxygen (primarily) and carbon dioxide (to a lesser extent) can be disrupted.
When interferons and other signaling substances activate a soldier of the immune system – white blood cells – and they begin to destroy cells infected with the virus, the body tries to repair the damage by creating scar tissue – for example, in the alveolar walls through which oxygen enters the blood vessels.
And although the “intentions” of the body are good, scar tissue does not allow oxygen to enter the blood vessels, and carbon dioxide does not allow them to exit, so it takes more time to exchange oxygen and carbon dioxide.
“The longer these processes take place in the lungs, the more difficult it is for a person to breathe. He begins to inhale air faster and more often, because the blood is poorly saturated with oxygen, and as a result, oxygen ceases to enter the body at all, ”explains Christian Weiss.
Fluid in the lungs interferes with breathing
At the same time, the virus can provoke irritation and inflammation of the lung tissue.
The blood vessels around the alveoli are so thin that holes appear in them, and the fluid resulting from inflammation begins to seep into the alveoli. Because of this, breathing becomes even more difficult, and the patient is connected to a ventilator.
When body cells stop receiving oxygen, inflammation spreads throughout the body, and the immune system is no longer able to fight the virus, a person dies.
However, despite the fact that COVID-19 can cause extremely serious complications, the estimated mortality from it is relatively low compared to, for example, SARS, from which 10% of all patients died.
In comparison, the death rate from coronavirus in Denmark is expected to be between 0.3 and 1%, according to the Department of Health.
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The article is written and prepared by our foreign editors from different countries around the world – material edited and published by Ordo News staff in our US newsroom press.