Environmental Susceptibility and Resistance to Coronavirus Disease-19 (COVID-19): A Review

Abstract

It is believed that certain environmental factors modulate coronavirus disease-19 (COVID-19). This review outlines the role of environmental factors in COVID-19 infectivity, spread, and severity. Relevant articles were retrieved from Google Scholar, SpringerLink, and Scopus, then pooled and duplicates removed with EndNote software. Available information reveals that temperature, relative humidity (RH), sunlight, pollutants, and population density modulate COVID-19 infectivity and pathogenicity. COVID-19 spread is promoted by low temperature (< 25 °C) and RH (< 40%), whereas it is inhibited by high temperature (> 25 °C) and RH (> 40%). Sunlight exposure alters the virus’s genetic material and boosts the host’s immune function by raising serum vitamin D (25-hydroxyvitanim D), reducing the virus’s viability and replication. Prolonged indoor stays with poor ventilation cause re-breathing of the air and increase carbon dioxide concentration, particularly in crowded rooms, predisposing to COVID-19. Pollutants, including particulate matter, nitrogen dioxide, ozone, and sulphur dioxide, may overexpress the virus’s receptor called angiotensin-converting enzyme 2 (ACE2), thereby increasing the virus’s infectivity. Pollutants may also induce inflammation of the respiratory tract, weakening the immune function and thereby increasing susceptibility to COVID-19. High population density increases body contact and thus susceptibility to the virus. To stem the incidence and mortality of COVID-19, the mentioned environmental factors must be kept at healthy levels.