Mutations, a normal way of adapting viruses - France 24

Paris (AFP)

Chinese authorities warned on Wednesday that the new coronavirus that appeared in the country "could mutate", a normal mode of operation for this family of viruses, but to watch closely because it could increase its potential of contagion.

- What does mutation of a virus mean?

Like living beings, viruses are endowed with genetic material (DNA or RNA), which can be subject to modifications when they replicate (mutations) or by exchanges between viruses (recombinations).

As viruses multiply quickly and in large numbers, they have greater potential than cellular organisms to generate mutations in a short period of time.

In addition, RNA viruses, like coronaviruses, are more likely to mutate than DNA viruses.

"Mutations are part of the normal operating mode for this type of virus," Vincent Enouf, deputy head of the National Reference Center for Respiratory Viruses (Institut Pasteur) in Paris, told AFP.

"Their survival depends on these mutations, which will allow them to adapt to their environment, to the different hosts they infect," he adds.

- What are the consequences of these changes?

Most often without consequence, these mutations can also give the virus an advantage or a disadvantage for its survival.

Certain mutations can thus allow it to replicate more quickly, to attack the body more severely (for example by infecting the lungs and not only the upper airways) or to infect new organs.

In the influenza virus, mutating a gene that controls the production of a protein on its surface can also allow it to attach more easily to the cells to be infected.

Certain mutations can also reduce the effectiveness of a vaccine, if the strain for which it was prepared has evolved in the meantime.

- Why should we watch them?

In the case of the coronavirus, which previously infected an animal, which remains to be identified, the passage to humans was probably facilitated by first genetic modifications, which allowed it to be recognized by receptors present on the surface. human cells.

But new mutations could allow it to adapt even better to its new host, with the risk that it will become more virulent and that it will spread more easily from one human being to another.

"It's hypothetical, but it must be monitored," explains Vincent Enouf.

The potential for the spread of an epidemic depends largely on the mode of contamination of the infectious agent (only by direct contact or also by air via saliva drops) and its degree of contagiousness.

However, the first genetic analyzes carried out on this new virus did not reveal any particularly worrying elements.

"The sequences observed" in viruses taken from different Chinese patients "are quite close to each other," notes the microbiologist.

This means that they have not yet undergone many mutations and "suggests that the transition to humans must have occurred quite recently", hypotheses which have yet to be confirmed, he underlines.

© 2020 AFP