Latitude impact on pandemic Sars-Cov-2 2020 outbreaks and possible utility of UV indexes in predictions of regional daily infections and deaths

The importance of two related factors (_) latitude and solar ultraviolet radiation (_) has been insufficiently recognized as determining the spread of pandemic Sars-CoV-2 outbreaks across the globe. In this study we provide evidence of the impact of latitude and investigate how daily RT-PCR diagnosed infections and deaths are quantitively correlated with the UV component of solar light. Here, we present regression analyses using daily national numbers from Austria and from Portugal with daily ultraviolet indexes of two selected locations in these territories, obtained from a satellite source. These countries, have similar surfaces areas and population size but Austria's mean latitude is 9° up-north. The equations derived from regression analyses of those two variables are comparable for both countries, fit best the fall (2(nd)) pandemic wave and can be a useful non-R(t) (ratio of transmission at a particular time) dependent predictive tool. Similar equations were derived for deaths that follow infections within a few weeks delay. Strong correlations depend on the size of the region/country from which infections are collected, the robustness of screening practices, ideally kept through weekends and holidays. Besides the forecasting usefulness of such correlations, these findings also suggest that covid-19 transmission co-exists with a Sars-Cov-2 specific UV-induced immunosuppression response. While in 2020, intensity of pandemic spring and fall waves reflect a solar UV-light modulation, we relate exceptional low temperature and humidity with additional waves, as the winter 2020/2021 3(rd) wave, felt in the western European countries. This work may help understanding this Pandemic phenomenon and dealing with similar catastrophes in the future.