The lung airway expression of both TMPRSS2 and ACE2 was found to be significantly upregulated in smokers compared with non-smokers, and in patients with chronic obstructive pulmonary disease compared with healthy subjects [70]; instead, children were found to have significantly lower expression of COVID-19 receptors in the upper and lower airways (nasal and bronchial) [70]. The gene discussed is TMPRSS2; the disease is chronic obstructive pulmonary disease.