No Association between UV Irradiance, Air Temperature, Heat Index and the Incidence and Transmission of COVID-19 in the United States

Background: The ongoing COVID-19 (Novel Coronavirus Disease 2019) pandemic caused by SARS CoV-2 is causing significant morbidity and mortality. Understanding the relationship between environmental factors like UV radiation, air temperature, heat index and the incidence and transmission of COVID-19 will help us predict geographic and seasonal variation in transmission. This in turn will help us allocate the limited resources appropriately.Aims and Methods: An epidemiological observational study design was utilized with data from 3053 counties across the United States. The data on average daily maximum air temperature and average daily maximum heat index were obtained from Centers for Disease Control (CDC) under the environment dataset. The data for Population weighted UV irradiance and COVID-19 case count by county were obtained from environmental health and toxicology dataset and case surveillance dataset respectively. The relationships between each environmental variable and COVID-19 case counts was visualized using Scatter plots and Spearman Correlation was calculated.Findings: The scatter plots with fit lines showed no correlation between UV Irradiance and COVID-19 case counts but showed a weak positive correlation between Air Temperature and Heat index and COVID-19 case counts (Fig.1). The Spearman rank correlation of the variables showed a coefficient of 0.099 (p<0.0001) for UV Irradiance suggesting no correlation and 0.186 (p<0.0001) for air temperature and 0.161 (p<0.0001) for heat index suggesting a very weak positive correlation (Table 2).Interpretation: Based on the county wise data across the United States, high levels of UV irradiance, air temperature and heat indices were not associated with decreased incidence or transmission of COVID-19 cases. Additional studies looking at the causal connection between environmental factors and COVID-19 transmission confounding for some of the significant variables is needed.Funding Statement: The author received no financial support for research, authorship, and/or publication of this articleDeclaration of Interests: The author declares no conflicting interests for this study.