The World Health Organization (WHO) has strict behavioral guidelines meant to curb the spread of SARS-CoV-2 -- the novel coronavirus that causes the COVID-19 disease -- such as covering one's mouth when coughing or sneezing, hand washing, and social distancing. A new study, however, highlights the potentially important role of smoking in both the spread and exacerbation of COVID-19.
Quitting smoking might reduce viral transmission and the risk of developing severe COVID-19 symptoms
First and foremost, COVID-19 is a respiratory illness, with studies indicating that its site of infection, viral replication, and virion shedding occurs within the respiratory tract.
The coronavirus is named after the crownlike spikes that protrude from its surface. It is through these spikes that the virus detects cells using the ACE-2 receptor, binding to it and injecting genetic material into host cells in order to replicate. These receptors are abundant in specialized cells of the respiratory tract, such as mucosal epithelial cells and lung alveolar tissue.
In 2009, researchers found that the syncytial virus, another respiratory virus, has a higher transmission rate and a greater incidence of disease severity in smokers.
Some have argued that perhaps such is the case for COVID-19 as well. Strictly behaviourally speaking, smoking involves repeated and frequent hand-to-face movements, which is the main mode of transmission for the novel coronavirus.
From an observational perspective, the countries that have reported the most sizable outbreaks of COVID-19 -- countries such as China, South Korea, and Italy -- also have high smoking rates, ranting from 19% to 27% of the population.
In an opinion piece for the British Medical Journal, David Simons (Ph.D. candidate in the epidemiology of emerging zoonotic diseases at the Royal Veterinary College), Olga Perski (Research Associate in the University College London's Tobacco and Alcohol Research Group), and Jamie Brown (Professor of Behavioural Science and Health and Co-Director of the UCL Tobacco and Alcohol Research Group) write that "definite evidence on whether current smokers are at increased risk of disease, morbidity, and mortality from COVID-19" is not available.
However, there are preliminary results that suggest just that. For instance, the authors of the BMJ article mention a recent study involving 1,099 confirmed cases of COVID-19, which reported that 12.4% of current smokers required intensive care unit admission or died compared to 4.7% among those who never smoked.
About 48% of men in China are smokers compared to just 3% of women. The WHO reports that the case fatality rate among males in Wuhan, China, was 4.7% compared to just 2.8% in women. It is plausible that these gender-specific differences in mortality might be owed, in part, to smoking.
In light of these findings, the authors of the new report strongly advise that public health messages aimed at curbing the spread of the novel coronavirus also include smoking cessation advice.
The ill-effects of smoking are well documented and reported. In the United States, cigarette smoking is linked to about 80% to 90% of lung cancer deaths. Smoking is also known to cause negative effects on heart function and circulation.
Really, there is no better moment to quit smoking and the COVID-19 pandemic might actually provide the perfect incentive for people to finally kick the habit. The fact that this pandemic is also causing a great deal of economic fallout -- and smoking is expensive in most developed countries -- also makes this a good time to quit.