Coronavirus and flu: these viruses that attack the lungs

The pandemic has come to remind us that certain viruses can seriously attack the lungs. And that after an infection, you have to re-educate your breathing.

Panting breaths, worried eyes behind oxygen masks, bodies lying down, intubated, ventilated, by the dozens in hospitals… With the coronavirus pandemic, tens of thousands of French people have had the terrifying experience of gasping for breath. “The earthquake caused by the pandemic showed us this brutally: the encounter of the respiratory system with a microbe can decimate a population, disorganize a society, simply because it destroys the lungs, responsible for bringing oxygen to the air to the blood, which it transports to the other organs, which all depend on it, ”recalls Professor Antoine Magnan, president of the French Society of French-speaking pneumology in an article published in Le Figaro. Pulmonologists obviously did not wait for the Sars-CoV-2 pandemic to know the enemies of breathing: influenza, respiratory syncytial virus, rhinoviruses but also other coronaviruses, all pathogens responsible for colds, bronchitis…


“Certain viruses, such as those of the flu, can cause pneumonia with acute respiratory distress syndromes: this diffuse, extremely sudden inflammation of the two lungs is responsible for the major deficit in blood oxygenation such as we have experienced with Sars- CoV-2»describes Professor Antoine Magnan.

Each year, of the 2 to 7 million people who get the flu, up to 1% are hospitalized for complications. Most of them concern the respiratory system. They can be directly caused by the flu virus but, most often, they are due to bacterial superinfection. “The flu destroys the cilia that line our respiratory system: they serve to mechanically eliminate germs. By the time these eyelashes are reforming, the bacteria will proliferate. This is what explains the flu “V”: patients have a fever, get better and then start a fever episode again. Their flu infection is cured but they have a bacterial superinfection”, describes Pr Claire Andrejak, pulmonologist at the University Hospital of Amiens. When pneumonias, viral or bacterial, are too virulent for the lungs and block the air supply, oxygen supplementation will give the body some time to win the battle of inflammation and scarring. .

” READ ALSO – Covid long: how to explain the persistence of symptoms months after infection?

What has changed with the arrival of Sars-CoV-2? Why did we witness such a tsunami? “To infect, this coronavirus strives to open a gateway, the ACE2 receptors, present everywhere in the body and in particular in the lungs. It was able to prosper because it found itself faced with a “naïve” population, that is to say without immune defenses to counter it. You have to imagine a house full of entrance doors (receivers) and without keys (immunity) to close them. The thief (the virus) was able to enter the house and do all the damage he wanted”illustrates Pr Sébastien Couraud, pulmonologist at the University Hospital of Lyon.

Pulmonary embolisms

Sars-CoV-2 has wreaked all the more havoc as it also causes blood clotting disorders because ACE2 receptors are found on the endothelial cells of blood vessels, “This is why, at the very beginning of the pandemic, we could not avoid deaths from pulmonary embolism because we did not know then that the virus was responsible for pulmonary thrombosis”explains Professor Chantal Raherison, pulmonologist at the Pointe-à-Pitre University Hospital.

The good news, according to doctors, is that when you manage to overcome this test, the lung is, in the vast majority of cases, repaired. “Contrary to what we feared at the very start of the epidemic, we are seeing very little pulmonary fibrosis, these scars on the lung which prevent it from fulfilling its function”explains Professor Antoine Magnan.

” READ ALSO – The long Covid, a new chronic disease

And yet, many months after their illness, many Covid-19 patients still complain of shortness of breath. “When I wanted to get back on my bike, I ran out of breath from the first shot.
of pedal. And as soon as I go up more than two floors, I get short of breath”, says Héloïse, the dynamic forty-something, who needed oxygen when she was sick in 2021. However, the scan of her lungs does not show any abnormality. How to explain it? Pulmonologists give several reasons. “There can be a deconditioning to the effort. You get an infection, you don’t move. However, a muscle that does not move consumes more oxygen and requires more. So we are more easily out of breath ”, explains Professor Claire Andrejak. The pulmonologist says she noticed a lot of shortness of breath linked to deconditioning following the first confinement. For these patients, the solution lies in respiratory rehabilitation. In other people, this shortness of breath is due to inappropriate hyperventilation. A phenomenon usually encountered in asthmatics. “Normally, you start to breathe faster, which corresponds to shortness of breath when you lack oxygen (in the case of pneumonia), or in a moment of anxiety. With Covid-19, you have breathless people who no longer have the reflex to adapt their breathing to the need for oxygen., describes Professor Andrejak. This inappropriate hyperventilation could be linked to a disturbance of the nervous centers of respiration. “In some people whose lungs had healed but could no longer move due to shortness of breath, brain imaging showed abnormalities in areas of respiratory control. However, we noticed a return to normal after a few months., observes Professor Bruno Housset, pulmonologist and former president of the Fondation du Souffle. For these people, the solution often involves rehabilitation to relearn how to breathe without thinking about it. “It can be done in town, but you have to find the right physiotherapist and know that it takes a long time”warns Professor Andrejak.


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