Can you really “catch cold” when the temperatures plummet?

• In a study published in recent days, American researchers demonstrate that it is indeed possible to "catch a cold".

• According to their work, winter temperatures would weaken the immune defense system housed in our nose.

• A track to better understand the mechanisms of respiratory infections and imagine future treatments to strengthen immunity.

"I caught a cold" (it's also true).

At the same time, it is cold, very cold, and like every year when the temperatures drop, everyone catches cold.

From the classic cold to the flu, bronchiolitis, nasopharyngitis and angina, without forgetting the Covid-19, the season of respiratory infections has begun and everywhere, people cough, sniffle, blow their nose and sneeze.

Except that until now, on the word of a doctor, we caught viruses and germs.

But "cold", no, such a thing did not exist.

Except that Science has just reviewed its copy.

in recent days

, exposure to cold affects the antiviral immunity of the nose.

How ?

explains everything to you.

The nose, immune barrier

If the notion of catching cold was hitherto demolished, it is because doctors and scientists explained the resurgence of respiratory infections in winter by a very specific seasonal habit.

“Generally, cold and flu season was thought to occur in the colder months because people live more indoors, where airborne viruses can spread more easily,” summarized Benjamin Bleier, co-author of study and surgeon at Harvard Medical School.

Now whether it is cape, rock, peak, peninsula or any mini, our nose shelters an army of small soldiers ready to regroup in a battalion and attack any virus that would come to tickle our nostrils.

Professor Mansoor Amiji, co-author of the study and professor at Northeastern University in Boston, discovered in previous work carried out in 2018 that cells in the nose release extracellular vesicles (EVs), a cloud of tiny particles attacking the bacteria upon inhalation.

"The best analogy is that of the hornet's nest," says the researcher.

Like hornets defending a nest from attack, VEs fly in swarms to attach to invaders and kill them.

An immune response weakened by the cold

As part of this new study, the researchers wanted to know if the nose secretes these EVs in the presence of a virus and if their effectiveness is affected by temperature?

To determine this, they used the nasal mucosa of volunteers (who were undergoing an operation to remove polyps), and a substance reproducing a viral infection.

They divided the nasal mucous membranes into two groups, with cells cultured in the laboratory at 37°C for some, and at 32°C for others.

Temperatures chosen from tests showing that the temperature inside the nose drops about 5°C when the outside air drops from 23°C to 4°C.

Results ?

Scientists have found that while the nose does indeed produce EVs to fight off viruses, a drop in the thermometer can affect their protective power.

Under normal body temperature conditions, EVs present "decoys" to viruses, to which the latter cling, instead of the cell receptors they would normally target.

And so block the infection.

But in cooler temperatures, EV production is not only less abundant, but also less effective against the viruses tested: two common rhinoviruses and a (non-Covid) coronavirus during winter.

In practice, “when the thermometer drops below 5°C, the functioning of this immune barrier, of the antiviral response of the ENT sphere is less effective.

Hence this expression of catching cold,

Future treatments and “ENT sling”

Until now, therefore, “there had never been a very convincing reason explaining why there is a clear increase in viral infectivity during the colder months”, underlined in a press release Benjamin Bleier, co-author of the study and surgeon at Harvard Medical School.

"This is the first quantitatively and biologically plausible explanation."

This work could make it possible to better understand the mechanisms of action of respiratory infections, but also to develop treatments to stimulate the natural production of EV, in order to be able to better fight these winter viruses, estimates Mansoor Amiji: "It is an area of research that interests us enormously, and we will undoubtedly continue on this path”.

In the meantime, “while we are in the middle of the meteorological winter and a triple epidemic of Covid-flu-bronchiolitis is raging, the best thing is to wear a mask, prescribes Dr Davido.

Not only is it a filter that protects against respiratory infections that are actively circulating, but it has a double protective effect: it also protects the nasal immune cells, by warming the atmosphere in the exhaled air, it is a kind of ENT scarf”.

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• Health

• Cold

• Virus

• Flu

• Bronchiolitis

• Covid-19