The flu has always existed. It is a virtual certainty today. “There is every reason to believe that influenza pandemics and seasonal influenza epidemics have existed for a very long time. Certain writings dating from Aristotle suggest influenza epidemics, texts from the Middle Ages report epidemic episodes At that time. It is very likely that influenza viruses have circulated in the human population with the introduction of new influenza viruses on the occasion of various pandemics for a very long time “, explains Professor Sylvie Van der Werf, head of the National Reference Center for viruses of the respiratory infections at the Institut Pasteur.
These writings never use the term “influenza” but they relate symptoms. High fever, chills, severe fatigue, headache and muscle pain. It is only very recently that the first so-called influenza viruses have been identified. “The first influenza viruses were isolated from pigs in 1932”, continues the specialist. A few years later, in 1944, Thomas Francis Junior, pushed by the American Army, developed a first effective vaccine. World War II had something to do with it. “
“There were flu among the soldiers, which is problematic for an army. This prompted a solution to be found to protect the troops from this infection, hence the idea of vaccinating,” she adds. The vaccine will finally be found thanks to work done on a chicken egg. “It is a chicken egg that has been fertilized. In which we will inoculate the virus into the cavity of the egg. The virus will be able to multiply in the cells present in this embryonated egg. The viruses produced are then harvested. in large quantities, which we will inactivate and that is what will be administered after the appropriate purification steps, ”summarizes the head of the National Reference Center.
The vaccine must evolve every year
Once administered to the patient, this solution induces antibodies against the various viral compounds. A major advance. Except here it is: this vaccine must evolve every year. “The influenza virus is an influenza virus that evolves all the time, permanently, by mutations and lack of corrections of its genome. There are four main types of human seasonal viruses. These are the pandemic H1N1 viruses that appeared in 2009 and have continued to circulate since. There are H3N2 viruses, both are type A viruses. There are type B viruses, of two types: victoria and yamagata. There are also type C and type D viruses. All of this is the flu, ”explains Vincent Enouf, a virologist at the Institut Pasteur.
The genomes are different. But the symptoms are the same. This is why every year, researchers from all over the world come together to try to prepare the vaccine that will be the most effective. “We try to anticipate as well as possible, it is the whole surveillance system in which we are registered. All the reference laboratories, all their data that we will detect and assess will make it possible to characterize each of the viruses. February, we put everything in common to check whether the viruses circulating at that time will have the capacity to evolve. It is a bet that has been taken. Others will always be the same. Then the WHO decides whether or not to change the vaccine composition for H3N2, H1N1 or type B viruses “, explains Vincent Enouf.
The flu vaccination is recommended every year, especially for frail people. Each year, 2 to 6 million French people are affected by an influenza virus.
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