Even if you are cured of a respiratory infection (flu, bronchiolote, covid-19, etc.), your cough can last for weeks or even months. Medical professor Kyle B. Enfield explains in The Conversation why it’s been taking so long.
It is difficult today to remember when was the last time we were in a public place without hearing someone cough. After three years of pandemic, the slightest cough makes us prick up our ears… or embarrasses us, if it’s ours!
With the increase, in the fall of 2022 and then during this winter, in the circulation of seasonal influenza viruses, Covid-19 and bronchiolitis (mainly caused by the respiratory syncytial virus or RSV), infections have multiplied , as well as associated sputum, cough and cough.
Coughing is indeed a common symptom of respiratory infections: it is the cause of 30 million medical consultations per year in the United States, 40% of which end in the office of a pulmonologist. Also, it is not uncommon to continue coughing long after an upper respiratory infection.
Persistent cough being so widespread, one could imagine that the medical profession has a long list of treatments adapted to its management. Unfortunately, this is not necessarily the case; it depends on the cause of said cough. When it comes to coughs that persist after a respiratory infection, time is usually a doctor’s best ally.
Why do we cough?
Doctors have long wondered why the duration of the cough can vary so much from one infection to another (whether of viral or bacterial origin). Why, as I see myself in my practice, do some patients develop long-lasting cough, while in others this symptom seems to disappear much more quickly? The answer is probably to be found in the differences that may exist between individuals: some people suffer from asthma, for example, others from chronic bronchitis…
A cough is the result of a complex process that begins with an electrical impulse occurring in the nerves that run through the airways, including the nose and throat. Two types of nerve receptors can trigger a cough in response to an external stimulus: receptors sensitive to certain chemical compounds, and receptors sensitive to mechanical stimuli (called mechanoreceptors). Chemical receptors are activated by odors and fumes; it is because of them that some people sometimes have a fit of coughing after inhaling the smell of spicy peppers sizzling on a hot pan. Mechanoreceptors respond to sensations produced by irritating substances, such as dust.
When these nerves are activated, the throat closes and the pressure in the chest increases. This increase in pressure results in an “explosion” of air and mucus, which propagates out of the lungs at more than 800 km/h. A speed that is almost twice that of the fastest cars on the planet!
Studies have shown that viral infections are capable of altering the sensitivity of the nerves involved. The inflammatory process that results from such an infection actually leads to the production of a molecule called bradykinin, which makes you want to cough. It has also been demonstrated that certain viruses themselves are capable of activating genetic modifications in the cells which increase the sensitivity of these processes, which leads to an increase in coughing.
But when the acute phase of the infection is over and you start to feel better, the body repairs the damage done in the lungs and airways by the inflammation. This rehabilitation attenuates the cough reflex. The molecular processes that made us cough and sneeze more frequently than usual stabilize and return to normal – at least in most cases. For some people, however, it may take longer than for others.
How long does the cough persist?
Doctors divide respiratory symptoms such as cough into specific categories. They consider that there are mainly three types of cough: acute, subacute and chronic.
Acute cough is what most people experience when they have a viral infection. A cough is considered subacute when it lasts more than three weeks after an upper respiratory illness. A chronic cough persists for more than 8 weeks. Most often, it is caused by asthma, post-nasal drip (mucus that accumulates in the back of the throat or in the back of the nose) and, perhaps surprisingly to some, by gastro-oesophageal reflux (ascent of part of the contents of the stomach into the oesophagus).
Post-infectious cough belongs to the category of subacute cough. Persistent after the end of a respiratory infection, when the other symptoms have disappeared, it can last for weeks or even months, then turning into a chronic cough.
Post-infectious cough is very common, and doctors have long struggled to determine how many people it affects. Estimates vary between studies: a study carried out in Japan on a small cohort of patients (124) revealed that among those suffering from a subacute or chronic cough, 12% had a respiratory tract infection.
With regard to Covid-19, current data indicates that only 2.5% of people affected by the disease developed a chronic cough after infection. This may seem small, but in reality it means that a large number of individuals could be affected: in the United States alone, at the beginning of February 2023 there were indeed more than 280,000 new cases of Covid-19 per week. . The actual number of people with chronic cough remains uncertain, however, because the studies that have looked into the question concerned small cohorts, which only concerned people who had consulted after catching Covid-19.
No Miracle Cough Cure
The American College of Thoracic Medicine and the European Respiratory Society have published guidelines to help clinicians make their diagnoses despite the uncertainties and lack of available data. Although they date from 2006, they are still the best guide available today for both physicians and their patients.
About half of people with a persistent cough eventually recover without any treatment. For patients who do not have this, the available data, although limited, suggest that inhalers, steroids, narcotics, and some over-the-counter medications can sometimes provide some relief.
In adults, however, evidence of effectiveness remains variable and limited. In my practice, I often prescribe a non-narcotic cough suppressant (benzonatate). This product works by “numbing” the nerves in the lungs and airways, which calms the cough reflex. In children, data on the efficacy of antitussive treatments are also very patchy, but studies have shown that over-the-counter medications and antihistamines were no more effective than placebos.
Some patients treat themselves with “homemade” remedies: many people use honey to soothe their cough, for example. There are indeed (limited) clues suggesting a potentially beneficial effect. One trial in particular found that, over a three-day period, honey was more effective than a placebo in reducing cough.
If your cough worries you, see a doctor
It is normal to be worried in the event of a persistent cough (a concern that a Google search will only reinforce…).
However unsatisfactory it is, however, keep in mind that most coughs will eventually resolve on their own. However, some cases justify making an appointment with your doctor without delay: rapid weight loss, night sweats, heavy sputum, bloody sputum… In rare cases, subacute and chronic cough can indeed be a sign of lung cancer or various chronic lung diseases.
Anyway, if the question of your cough worries you, and you feel a need for information or advice, do not hesitate to consult. Millions of other people are in the same situation as you every year…
Kyle B. Enfield, Associate Professor of Medicine, University of Virginia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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