Posted by Fatima Khalil
Tuesday, February 14, 2023 04:00 PM
Cough is a common symptom of many infections Respiratory systemCough is a complaint that leads to an estimated 30 million visits to the doctor each year in the United States, according to Science Alert.
The cough after an upper respiratory infection usually goes away in time, but sometimes it can last a long time.
How does coughing occur?
Doctors wondered why the duration of a cough varies so much after a viral or bacterial infection of the upper respiratory tract.
The answer likely lies in differences between people, such as whether you have a condition such as asthma or chronic bronchitis.
Some patients develop a lingering cough, while others seem to clear up the cough much sooner, with no clear explanation.
Coughing is caused by a complex process that begins with an electrical impulse between the nerves within the airways, including the nose and throat.
There are two types of nerves that can trigger a cough in response to external stimuli: chemoreceptors and mechanical ones called mechanoreceptors.
Chemoreceptors that respond to smells and fumes are the reason people sometimes cough after inhaling the sizzling of hot peppers on a hot frying pan.
When these nerves are activated, the throat closes and pressure builds up in the chest. This build-up of pressure causes the air and mucous membranes in the lungs to explode at speeds of about 500 miles per hour – twice as fast as the fastest cars in the world.
Studies show that viral infections alter how sensitive these same nerves are. When you have a viral infection, the resulting inflammatory process produces a molecule called bradykinin that triggers the urge to cough.
It is known that the virus itself can activate genetic changes that increase the sensitivity of these nerve pathways, leading to more coughing.
But when the acute phase of the infection is over, and you start to feel better, the body repairs the damage caused by the inflammation in the airways and lungs.
A subacute cough lasts for three weeks or longer after an upper respiratory illness.
A chronic cough is a cough that lasts more than 12 weeks.
The most common cause of chronic cough is asthma, postnasal drip, and possibly reflux.
A post-infectious cough is a type of subacute cough that is a persistent cough that many people experience after they have overcome a respiratory infection.
It can last for weeks or months and can develop into a chronic cough.
Because postinfective coughs are so common, doctors have worked for a long time to determine how many people have a cough that persists after other symptoms are gone.
These estimates vary between studies. One small study in Japan found that among people with subacute and chronic cough, 12 percent resulted from a respiratory infection.