Understanding factors impacting deaths from COVID-19 is of the highest priority. Seasonal variation in environmental meteorological conditions affects the incidence of many infectious diseases and may also affect COVID-19. Ultraviolet A (UVA) radiation induces release of cutaneous photolabile nitric oxide (NO) impacting the cardiovascular system and metabolic syndrome, both COVID-19 risk factors. NO also inhibits the replication of SARS-CoV2.To investigate the relationship between ambient UVA radiation and COVID-19 deaths.COVID-19 deaths at the county level, across the USA, were modelled in a Zero Inflated Negative Binomial model with a random effect for States adjusting for confounding by demographic, socioeconomic and long-term environmental variables. Only areas where UVB was too low to be inducing significant cutaneous vitamin D3 synthesis were modelled. We used satellite-derived estimates of UVA, UVB and temperature and relative humidity. Replication models were undertaken using comparable data for England and Italy.The Mortality Risk Ratio (MRR), in the USA, falls by 29% (40% -15% (95% CI)) per 100 (KJ/m2 ) increase in mean daily UVA. We replicate this in independent studies in Italy and England and estimate a pooled decline in MRR of 32% (48%-12%) per 100 KJ/m2 across the three studies.Our analysis suggests that higher ambient UVA exposure is associated with lower COVID-19 specific mortality. Further research on the mechanism may indicate novel treatments. Optimised UVA exposure may have population health benefits.
M Cherrie, T Clemens, C Colandrea, Z Feng, D J Webb, R B Weller, C Dibben