Implications of Monsoon Season & UVB Radiation for COVID-19 in India Manuscript

Abstract

Background: India has recorded 66,333 deaths over 36 administrative regions placing India third in the world after the US and Brazil for COVID-19 deaths as of 2 September 2020. Studies indicate that south-west monsoon season plays a role in the dynamics of contagious diseases, which tend to peak post-monsoon season. Recent studies show that vitamin D and its primary source Ultraviolet-B radiation (UVB) may play a protective role in mitigating COVID-19 deaths. However, the combined roles of the monsoon season and UVB in COVID-19 in India are still unclear. In this observational study, we empirically study the respective roles of monsoon season and UVB, whilst further exploring, whether monsoon season negatively impacts the protective role of UVB in COVID-19 deaths in India. Methods: We use a log-linear Mundlak model to a panel dataset of 36 administrative regions in India from 14 March 2020 - 8 August 2020 (n=4005). We use the cumulative COVID-19 deaths as the dependent variable. We isolate the association of monsoon season and UVB as measured by Ultraviolet Index (UVI) from other confounding time-constant and time-varying region-specific factors. Findings: After controlling for various confounding factors, we observe that the monsoon season and a unit increase in UVI are separately associated with 12.8 percentage points and 2.0 percentage points decline in growth rates of COVID-19 deaths in the long run. These associations translate into substantial relative changes. For example, the current monsoon season, that has been going on for two weeks, is associated with a reduction in growth rates of COVID-19 deaths of 59%, whereas a permanent unit increase of UVI is associated with a reduction in growth rates of COVID-19 deaths of 37%. However, the current monsoon season, also reduces the protective role of UVI by 16.3% [0.33 percentage points], plausibly due to lower UVB exposure. Interpretation: We find independent protective roles of both the monsoon season and UVI in mitigating COVID-19 deaths. Furthermore, we find evidence that monsoon season is associated with a significant reduction in the protective role of UVI. The protective role of monsoon season is plausibly due to limited outdoor activities of people. Our study outlines the role of the monsoon season and UVB in COVID-19 in India and supports health-related policy decision making in India.

Is ultraviolet Radiation a Confounding Variable for COVID-19 in India?

“…In general it is found that higher rate of increase in UVI is associated with the lower death counts. Similar results are also observed by 33 . The anticorrelation established the fact that in a city like Ahmedabad, the number of mortality counts is found to be lowest because % growth in UVI is highest (22%).…”

“…The UVI has indicated a minimal increase for Mumbai in 2020 as compared to the previous three years average. There are various meteorological confounding factors which affects the morbidity and mortality of COVID-19 33 . According to 34 , relative humidity and absolute humidity showed a moderate positive correlation with the daily COVID-19 cases in few cities of India.…”