What is a virus?

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By: Simon Rozé Follow

Covid-19 is the name of the disease caused by a coronavirus whose official name is SARS-CoV-2, like AIDS is the name of the disease caused by HIV. Both HIV and SARS-CoV-2 are viruses. But what is a virus?

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It is a vast subject that touches a large section of biology. To start: we, the animals, the plants, are beings made up of cells, an envelope. Inside these cells, there is what is called the nucleus. It contains genetic information, like DNA. There are also a whole bunch of structures that allow the cell to function and fulfill its role in the body.

A cell is capable of "reproducing". If given energy, a mother cell can divide into two daughter cells. It's called mitosis. There are also organisms composed of a single cell, the vast majority of bacteria for example. So we say that they are single-celled, they too can duplicate.

But viruses do not have this ability. They are much simpler and much smaller. A virus is a few strands of genetic information protected by a membrane. They do not have all the machinery of the cells and above all they are incapable of mitosis. They cannot divide on their own. It is in particular for this reason that they are not always considered as living beings.

• How do they manage to invade a living organism?

They are "pirates". They have the ability to enter cells. They drop their genetic material there which will divert all cellular machinery to their profit. The attacked cell will then have to create copies of the virus instead of fulfilling the missions that it normally has.

There are several families of viruses, several ways to "hack" a cell. The bottom line is that in general a type of virus attacks a species, a kind of cell in particular. They are specialized.

• So coronaviruses target the respiratory systems?

Yes, they infect cells there, they replicate there, and disrupt their functioning. It is for this reason that they cause respiratory distress, but contrary to what we can hear, they are not our enemies. They don't knowingly do this in order to harm us. The virus “lives its virus life”. He goes where he can go.

As proof, coronaviruses are generally zoonotic. They target animals first. So they live their lives, and depending on their replication, they sometimes change a little. This is called a mutation. It happens randomly. Sometimes one of these mutations can open a door, giving them access to other types of cells. They then have the opportunity to infect humans. A new path opened for them, they just took it.

► Also read: Coronavirus, in search of the guilty animal

• What is the way to get rid of it?

Since viruses use cells to reproduce there, it is difficult to kill them without killing the host cell. By definition, antibiotics are useless against viruses. They target mechanisms of bacteria that viruses do not have. There are, however, drugs called antivirals, which can disrupt the replication of the virus.

But there is a way to prevent them: it is the vaccine. It involves training our immune system so that it can cope with a future attack, but it is complicated. For example, we still don't have an HIV vaccine.

On the other hand, there is a precautionary method which is particularly effective against coronaviruses, repeated for weeks, it is the soap, for a chemical reason. The envelope that protects the genetic information of coronaviruses is made of what is called lipids, fat. What makes up soap is very effective in getting rid of fat, which therefore breaks the envelope of the virus.

In short, we can never repeat it enough, wash your hands!

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