The virus uses people to multiply. The next steps show how it works – and why it makes you sick.
Coronaviruses usually enter the throat through the air we breathe – trapped in droplets or aerosols.
The SARS-CoV-2 virus is only 140 nanometres in size. A human hair is 500 times as thick. Research is currently being carried out around the world into exactly how the virus infects people. Here you can see the first results of the research – and what makes SARS-CoV-2 so dangerous.
This is how the virus enters the cells.
The genetic information of the virus is stored in his RNA.
(Ribonucleic acid (RNS for short; English RNA for ribonucleic acid) is a nucleic acid composed of a chain of many nucleotides. In certain types of viruses, the biomolecule is the carrier of the genetic information, i.e. the material basis of the genes. An essential function of the RNA in the biological cell is the conversion of genetic information into proteins).
With 29,900 nucleotides, it is very long compared to other RNA viruses: twice as long as influenza, three times as large as HIV. RNA is 96% the same as that of a coronavirus found in bats. It is a kind of control system of the virus. It causes cells to produce new viruses. Because without the cells the virus cannot multiply – it depends on it.
The virus has an outer shell. This includes three important Proteins (Proteins): a) envelope proteins and b) membrane proteins give the virus shape and stability.
A third protein gives the corona virus its name. The so-called spike proteins stick out of the shell like spikes. Under the microscope it looks like a crown, in Latin corona. With their help, SARS-CoV-2 docks the cells – the beginning of reproduction.
When the spikes come close to the receptor, part of it flips out. This is a special feature of the virus and possibly an explanation of why it spreads so quickly. This is because the peak of SARS-CoV-2 binds many times more strongly to the receptor than its predecessor SARS-CoV, which appeared in 2002.
When the peak and the virus receptor are linked, the cell activates a process that transports the virus to the inside of the cell. The cell membrane
The cell membrane is called the biomembrane, which is unique to every living cell and which surrounds and delimits the cell interior and preserves its interior environment. The cell membrane rotates inwards. With the help of other proteins, a bladder is narrowed.
In the cell, the bubble opens. The virus releases its RNA into the interior of the cell, in the so-called cytoplasm. In this way, a control programme enters the cell, which becomes its undoing.
The RNA is read by certain parts of the cell, the ribosomes. These are the cell’s protein factories. They follow the building instructions in the RNA code and produce virus components and other proteins that SARS-CoV-2 needs for propagation.
Another protein, called RNA polymerase, is also used to produce copies of the viral RNA. This allows the components to be assembled into new viruses. The membrane protein of the virus ensures that the shell is properly formed. It is composed of membrane parts of the cell’s endoplasmic reticulum.
Gradually, the new viruses are transported out of the cell. The host cell is not destroyed. This allows a cell to produce millions of new viruses before it dies.
The intruder will not go unnoticed. It activates the defence of the body, the immune system. The purification cells are part of it. They devour some viruses and break them down into their individual parts. All defence needs energy. The body temperature rises, to a fever.
But not all coronaviruses are eaten. Many get through. They infect more cells. First in the throat, later in other parts of the body. For researchers it is still unclear whether the virus moves cell by cell or whether it can go directly from the throat to the lungs, for example.
A chain reaction begins. The infected cells produce even more viruses. But the cells report the uninvited guests to their environment via messenger substances. That calls the killer cells into action. They attack infected cells and destroy them. And they release even more messenger substances to attract more immune system helpers.
In its zeal to fight the invaders, the immune system can overreact. At the same time, more and more cellular remains are piling up. A secretion of immune cells and cell debris is formed.
This is how the coronavirus attacks the whole body…
All messenger substances, called cytokines, are actually intended to help the body get rid of the virus. But they can also be a reason why SARS-CoV-2 makes us so sick. This is because the virus causes the cells to produce particularly large quantities of cytokines. Our immune system is warming up. It sends in more and more immune cells, causing more and more serious inflammation.
Covid-19 is the name of the disease that causes SARS-CoV-2.
It starts in the throat. That is why coughing is often one of the first symptoms. Fatal! The virus is expelled from the body at high speed. When things go badly, the cycle starts again – in another person’s body.
SARS-CoV-2 also infects the lung cells. If the immune system reacts too violently to the attacker, the alveoli fill up with the fluid from the immune cells. This is where oxygen from the air we breathe is otherwise introduced into the blood. When the alveoli are full, they no longer function. This results in shortness of breath and severe pneumonia.
The heart can also be affected. Many seriously ill patients have been diagnosed with an inflammation of the heart muscle. It is unclear whether the virus directly damages the cells of the heart – or whether the immune reaction causes the damage.
A disturbed sense of taste and smell can also be one of the early symptoms of Covid-19 disease. This could indicate that the virus affects our nervous system and may even migrate to the brain. There too, the cells have docking sites for ACE2. But whether the virus really infects them or whether the disturbances in the nervous system are a result of the immune response is still unclear.
Autopsies have shown that the blood vessels are also affected. The result: lumps form in the blood, thrombosis develops. If they travel through the body, they can clog up organs. This leads to a heart attack in the heart and a stroke in the brain. If the small blood clots block the lungs, a pulmonary embolism develops.
Where active substances can be applied
In the course of the pandemic it became clear how different the symptoms that can be SARS-CoV-2 triggers can be. Diarrhoea, rash, kidney failure – new effects are constantly being discovered. Research is being conducted all over the world to find out why this is the case, day and night, as part of probably the largest and fastest research campaign in recent history. But above all, they are looking for an antidote.
An antidote could intervene at various points in the virus cycle you have just explored. One possibility would be to use drugs that have been known for a long time in order to prevent the production of too many messenger substances. This could reduce the inflammation and thus ensure a milder course of the Covid-19 disease.
A second strategy is to sabotage the virus’ reproductive process. The drug Remdesivir was originally developed for the treatment of Ebola. It disguises itself as an RNA building block in the cell. When it is incorporated into the RNA of the virus, it remains attached to the protein that composes the new RNA. This means that the genetic information can no longer be duplicated. Reproduction of the virus is stopped. Other research approaches try to disrupt the production of other virus components in the cell.
Research has also focused on the spikes. This is where the body’s own enzymes dock, speeding up the penetration of SARS CoV-2 into human cells. For example, the enzyme furine, which activates the newly built spike proteins in the cell in such a way that the new viruses can penetrate even better into new host cells.
Some scientists hope that this is a good starting point for the search for a vaccine. A coronavirus without the perfect berth for the enzyme furine could spread more slowly in the body. The virus would then be so weak that it causes no symptoms, but the immune system would still be able to produce antibodies, as is usually the case with live vaccinations with weakened pathogens.
Although thousands of researchers in many countries around the world are looking for these solutions, their analyses usually take a very long time. If they are successful and discover a vaccine or drug, the production processes still need to be adapted or developed. Then there is the negotiation of how and by whom all the research will be paid for – and who will be the first to receive the antidotes.
Until then, only interpersonal measures against the spread of the virus will help.
Take care of each other!