Expert interview on coronavirus infection: What happens in the body?

The coronavirus called SARS-CoV-2 is keeping the world in suspense: Many people fear contracting the virus and are afraid of the consequences. Like other viruses, the coronavirus uses the cells of infected people as a host to replicate, causing the affected cell to die or be involved in its function. In the case of SARS-CoV-2, this can sometimes have serious consequences. But even if countless deaths have already been recorded as a result of COVID-19, the disease can take very different courses. But why is that, and what happens in the body during an infection?

Lung specialist Dr Barczok, in an interview

We have Dr Michael Barczok, lung specialist and deputy chairman of the professional association of Pneumologists in Baden-Württemberg, who was asked about this. In an interview, he explains how infection with the coronavirus works, what happens in the body in the event of a serious illness and why the course of the disease can be so different.

The interview was conducted in April 2020 and reflects the state of knowledge.

 

Which areas of the body are typically affected by the coronavirus?

dr Barczok:  Many viruses have specialized in the upper or lower respiratory tract, although other organs can also be the focus. The coronaviruses, i.e., the pharynx, mainly affect the upper respiratory tract. The SARS-CoV-2 virus is no exception.

In about 80 per cent of cases, there are primarily mild symptoms in the area of ​​the upper respiratory tract, and a dry cough also occurs. In about 20 per cent of cases, however, other organs are involved, especially the lungs, but the heart, kidneys, liver, brain, and intestines can also cause problems.

It becomes life-threatening when the lung tissue is involved to such an extent that the body can no longer be supplied with sufficient oxygen.

What does a typical course of the disease look like?

Dr Barczok: In many cases, the viruses remain in the upper respiratory tract. The disease is hardly noticed and runs like a banal respiratory infection, maybe causing a bit of fever and exhaustion, but you feel fit again quickly. This stage of the disease usually goes through in one to two weeks without complications.

Even with a mild course, however, high fever can occur for several days, combined with coughing and often a temporary loss of smell and taste. Adequate fluid intake is essential here, fever-reducing measures in the case of a high fever, appropriate medication if necessary, preferably paracetamol and light exercise to prevent thrombosis. The general practitioner should be informed and, in the knowledge of the patient’s particular problems, provide appropriate information or intervene.

It is positive that at least 80 per cent of the patients survive this typical phase without serious complications. However, every fifth patient suffers from severe symptoms with high fever, sometimes an intense feeling of illness and often involvement of other organs, especially the lungs and heart.

 

What happens in the body with such a severe course, and what are the possible consequences?

Dr Barczok: In a severe course, the virus makes its way deep into the lungs, multiplies rapidly in the lung tissue and the alveoli and seems to be able to attack other organs such as the heart, liver, kidneys and brain in this phase and cause inflammatory reactions to give.

These inflammations sometimes increase the damage because local swelling and tissue destruction can occur. This can lead to a drastic drop in cardiac output or cardiac arrhythmia in the heart. In the vessels, the inflammation threatens to disrupt the blood microcirculation, resulting in oxygen not being appropriately transported from the lungs to the body.

In the lungs themselves, the inflammation leads to swelling of the air sacs, which may also fill with fluid and can no longer fulfil their function of releasing oxygen into the blood and removing used CO2 from the body again.

The greater the extent of these disorders, the more severely the lungs may have been damaged from earlier, and the more fatal this situation is for the entire organism. Unfortunately, the disease is deadly for about 0.5 to one per cent of all those infected. According to everything we know, older people are particularly affected, or people with certain previous illnesses such as obesity, COPD, heart failure, diabetes and patients who are on anti-immune therapy. Smokers also appear to be at particular risk.

Can COVID-19 cause permanent damage?

dr Barczok: We still know little about long-term consequential damage . However, we have to assume that permanent damage to the body and psyche can occur, especially after prolonged ventilation therapy.

In particular, it is becoming increasingly clear that permanent functional losses, especially in the lungs, are to be feared, which will continue to exist for at least a long time and will make drug therapy necessary. But permanent damage could also occur to the heart.

The same applies to the central nervous system, the liver or the kidneys. Many more severely ill will need rehabilitation before they can return to their former lives. However, it is already clear that for some patients, being discharged from the hospital will not mean they can continue living as they used to.

After all, according to the current state of knowledge, all infected people can assume that after the symptoms of the disease have subsided, they can be reasonably safe from another infection for a more extended period.

Why does the disease progress so differently overall?

Dr Barczok: Why the disease progresses so differently in many people is the subject of intensive research projects. A whole bundle of factors is undoubtedly responsible for this. In addition to genetic factors and the level of development of the immune system, which leads to a relatively mild, uncomplicated course, especially in children, the number of viruses one is acutely confronted with also plays a role. If you breathe in billions of virus particles at once, the reaction situation for the body is different than if it only has to deal with a few pathogens.

It may also affect whether you have recently been infected with other less virulent coronaviruses, which does not lead to complete immunity. Still, it may allow the immune system to kick in faster. We know that some medications and, above all, smoking make it easier for SARS-CoV-2 to access them and that smoking also disrupts the “waste removal” in the bronchi.

Overall, the better the organism is set up, the healthier one lives, and the better the conditions for the body’s defences to successfully defend itself.