Having a cough is your body’s way of eliminating irritants that enter its airways. This protective mechanism of our bodies is one of the most common symptoms of an upper respiratory tract infection (common cold or flu). Seeing that COVID-19 is a viral respiratory infection, it is not surprising that having a cough is one of its common symptoms.
What causes a COVID-19 cough?
Coughs, in general, have multiple triggers, some of which include:
- Inflammation (e.g. infection)
- Mechanical (e.g. foreign body)
- Chemical (e.g. cigarette smoke)
- Thermal (e.g. cold air)
These triggers can provoke nerves distributed in the airways and stimulate the cough centre in the brain to trigger a cough reflex.
Similarly, when coronavirus invades the airways, the body reacts by initiating a cough reflex. During this, the cough impulse stimulates the respiratory muscle to perform a deep inspiration, followed by a forceful contraction, resulting in an explosive outflow of air.
COVID-19 usually causes a dry cough, but some people may have a chesty cough (cough with phlegm).
Persistent cough after COVID-19
Cough caused by COVID-19 is usually acute and will slowly disappear during recovery. However, sometimes it can persist and become a chronic cough, defined as a cough lasting more than 8 weeks.
Globally, the prevalence of a persistent cough after an acute COVID-19 infection can be variable depending on the severity of the initial infection and the duration of the cough can last for weeks, months or even up to a year.
Global statistics have reported that among symptomatic patients, the prevalence of a persistent cough is 11.4% at 5 weeks (self-reported) and 10% at 4 months after the onset of symptoms (non-hospitalised patients). Comparatively, hospitalised patients have a higher prevalence of persistent cough where 15·4% of patients reported the symptom after 2 months and 2.5% after 1 year after being infected with COVID-19.
During a COVID-19 infection, our body's immune system fights off the pathogen by undergoing a process called inflammation, which can cause fluid accumulation and swelling of tissues. The process can last for a long time even after the virus has been destroyed, causing lingering symptoms.
Why do I keep coughing after COVID-19?
There are 4 possible inflammation-related reasons why cough persists after COVID-19:
Postnasal drip. The nasal passages and sinuses stay inflamed, and the fluid produced drips down the back of the throat, stimulating the cough impulse.
Lower airway and lung infection. The cough reflex is triggered by swollen tissues to clear the fluid in the lower respiratory tract.
Neuronal mechanisms of hypersensitivity. The virus can cause neural tissue inflammation, either centrally (the brain) and/or peripherally (nerves) which triggers the cough reflex.
Interstitial lung disease. The lung tissue is injured and scarred from the inflammation. This condition is usually serious and requires medical attention.
A persistent cough after COVID-19 is usually grouped with other conditions such as fatigue, shortness of breath, and chest pain, under an umbrella term called “long COVID” when these symptoms persist for 4 or more weeks after the acute infection.
There is still a lack of evidence to explain the causes of long COVID although some studies suggest being female, having respiratory comorbidities, and the severity of COVID-19 experienced by the individual could be contributing factors.
Is my lingering cough after COVID-19 contagious?
A persistent cough after COVID-19 does not mean you are still contagious, even if you still test positive for the virus. In asymptomatic, mild, and moderate COVID-19 patients, the virus is no longer infectious after 10 days of symptom onset.
The Centers for Disease Control and Prevention (CDC) in the US recommends an isolation period of at least 5 days, followed by the wearing of a mask until the 10th day. However, in severe COVID-19 patients, the virus may remain infectious for up to 20 days, requiring a longer isolation period of at least 10 days.
How do I recover from a cough after COVID-19?
A persistent cough, though not necessarily detrimental to physical health, can affect your mental health due to the stress it can produce. Here are some recovery tips:
Keep your airway moisturised. A moist airway reduces the triggering of the cough reflex and may increase the threshold of hypersensitivity-induced cough over time. Ensure that you are adequately hydrated by frequently drinking water. Mixing honey and lemon into lukewarm water can help keep your airway moisturised. Also, inhaling steam in a hot shower or via a vaporiser is another good way to keep your airway moisturised.
Practise chest physiotherapy. This includes postural drainage, chest percussion (clapping), deep breathing, and the huff coughing technique. Keeping your head above your chest during sleep will also help reduce coughing during your sleep.
Avoid cough-triggering substances. Examples include tobacco smoke, smoky or hazy atmospheres, cold air, and strong smells like that of air fresheners, scented candles, perfumes, and deodorants.
Take over-the-counter medication and lozenges. Nasal sprays and saline rinses are particularly helpful for cough induced by post-nasal drips.
Practise a healthy lifestyle. Ensure you get enough, exercise regularly, and have a healthy diet in order to boost your body’s immunity. Traditional Chinese Medicine, or TCM, can also be helpful as it restores the balance of energy, such as qi, in the body. This can bring relief to cough and nausea that is often experienced by patients with long COVID.
Having a persistent cough after COVID-19, while not common, is a normal phenomenon and does not necessarily cause severe health complications. However, if your symptoms worsen, talk to your healthcare provider and get the appropriate treatment.
Article reviewed by Dr Joy Lim, acting medical director at IHH Healthcare Singapore, and Physician Lim Tze Chao, Traditional Chinese Physician at Parkway Shenton
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