Those with comorbidities, like cardiac and liver ailments, and smokers are more prone to fall prey to Covid-19, say doctors. The World Health Organisation (WHO) has listed smoking as one of the major risk factors for coronavirus as it suppresses immune functions of body.

Smokers have higher expression of ACE2 (angiotensin converting enzyme 2) that signals inflammation and also more secretory cells making them susceptible to infections.

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ACE2, attached to the outer surface of cells in lungs, arteries, heart, kidney and intestines, also serves as the entry point for coronaviruse, including SARS-CoV-2 (Covid-19).

“Studies suggest Covid-19 virus interacts with specific human receptor, known as hACE2 (human angiotensin converting enzyme 2), that infects lungs and nasal mucosa. Hence, it’s highly recommended that one stays away from smoking to stay safe,” said Dr Latha Sharma, consultant pulmonologist, KIMS Hospitals.

According to a University College London study, smokers are 1.45 times more likely to have severe complications compared with non-smokers and those who quit smoking.

Also, critically ill Covid-19 patients with chronic obstructive pulmonary disease (COPD) had 63 per cent risk of severe disease and 60 per cent risk of mortality, while critically ill patients without COPD had only 33.4 per cent risk of severe disease and 55 per cent risk of mortality.

“While 60 plus years, diabetes and high blood pressure are seen as the likely comorbidities for a Covid-19 patient, a review of studies by public health experts convened by WHO, found that Covid-19 may turn more severe in smokers than on-smokers,” said Dr Nishant Sinha, senior consultant pulmonologist, Continental Hospitals.

“Smoking impairs the capacity to fight infections due to damage of Cilia, tiny hair like structures in the airways. Tobacco smoke is also a major risk factor for non-communicable ailments, like cardiovascular and respiratory diseases, cancer and diabetes. Coronavirus infection turns severe in people with these ailments,” he said.

“Smoking negatively impacts lung health, inhibits body’s responsiveness to infections, and suppresses immunity. Sound epidemiological evidence that smoking increases the risk of viral lung and throat infections led researchers to posit that smokers are at increased Covid-19 risk. Smoking is associated with increased risk of virtually every other respiratory infectious diseases,” said Dr Ravindra Nallagonda, senior consultant in pulmonology and critical care medicine, Aster Prime Hospital.

According to him, smoking destroys important defences, like airway cilia that helps move particulate out of the airway. Excess and thicker mucus prevents expectoration of debris, bacteria and viruses. Over time, it breaks down the vital lung tissue needed for life.

“Many have suspected a particularly strong correlation between smoking and Covid-19 second to smoking’s effect on increasing ACE2 receptors in lungs,” he said.

Tobacco smokers (cigarettes, water pipes, bidis, cigars, heated tobacco products) may be more vulnerable to contracting Covid-19 as smoking involves contact of fingers (and possibly contaminated cigarettes) with lips that increases the possibility of transmission of virus from hand to mouth.

According to a study published in the New England Journal of Medicine in February, against non-smokers, smokers are 2.4 times more likely to be admitted to an intensive care unit, need mechanical ventilation or die.

According to doctors, electronic nicotine delivery systems and electronic non-nicotine delivery systems, commonly referred to as e-cigarettes, are harmful and increase the risk of heart disease and lung disorders.