COVID-19 and Sunlight: Impact on SARS-CoV-2 Transmissibility, Morbidity, and Mortality

Coronavirus disease 2019 (COVID-19) has already affected millions of people worldwide. There are reports of SARS-CoV-2 transmission as a consequence of environmental contamination. The SARS-CoV-2 laden infective droplets can actively persist on the surface of different materials for several hours to days. Sunlight can affect the stability of SARS-CoV-2 in these aerosols and thereby have an impact on the decay rate of the virus. Solar radiation might play an important role in inactivating SARS-CoV-2 that persists in different surfaces and the environment. Among the different climatological factors, ultraviolet radiation was found to have an important role in determining the spread of SARS-CoV-2. Although ultraviolet radiation C (UVC), UVB, UVA, visible light, and infrared radiation possess germicidal properties, human CoVs including the recently emerged SARS-CoV-2 are inherently sensitive to UVC. However, the successful decontamination using other wavebands requires higher dosages and longer administration times. Furthermore, studies have also identified association between COVID-19 fatalities and the latitude. The intensity of sunlight is highest near the equator, and therefore populations in these regions with more regular exposure to sunlight are less susceptible to vitamin D deficiency. This article has analyzed the potential impact of sunlight in reducing SARS-CoV-2 transmissibility, morbidity, and mortality. It is evident that there exists an interesting link between sunlight exposure, latitude, and vitamin D status with COVID-19 incidence, fatality and recovery rates that requires further investigation.