Relationship Between Smoking and Viral Pneumonia: A Narrative Review

Viral pneumonia affects about 200 million people each year. Viral pneumonias have a seasonal pattern and are more common among children and the elderly. The most common virus in children is respiratory syncytial virus (RCV) and it is the influenza virus in adults. The world has been fighting the COVID-19 pandemic since December 2019. Among all the epidemiological risk factors, the role of smoking as a risk factor for pneumonia is controversial. Cigarette smoke contains about 5000 chemicals that weaken the defense mechanisms of the respiratory system and increase the risk of various respiratory infections. The present review study was carried out on 105 articles that were obtained from searches in Scopus, PubMed, and Google Scholar search engines using the keywords viral pneumonia, COVID-19, influenza, cigarette, smoking, respiratory syncytial virus, and SARS-CoV-2. A total of 55 articles that focused on the effect of smoking on the incidence and mortality of pneumonia due to RSV, influenza, and coronavirus were selected. Exposure to secondhand smoke makes children more susceptible to RSV infection. Smokers are also more likely to become infected and die from the flu. The effect of smoking on the risk of COVID-19 is controversial. In this regard, the results of a number of studies show that smokers are at a greater risk of developing COVID-19 infection and death. However, there are other studies suggesting that smoking has no effect on COVID-19 infection and that smoking reduces the risk of developing COVID-19.