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

TL;DR: In this paper, the authors empirically studied the respective roles of monsoon season and UVB, whilst further exploring, whether the negative impact of the tropical season negatively impacts the protective role of UVB in COVID-19 deaths in India.

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.

Summary

1 Introduction

• The authors empirically describe the roles of the monsoon season and further explore, whether monsoon season result in a reduction in the protective role of UVB in COVID-19 deaths in India.
• After controlling for various confounding factors, the authors observe that in the long run the monsoon season and a unit increase in UVI are separately associated with.

Radiation & COVID-19 Deaths in India

• Studies indicate that the monsoon season and post-monsoon season may be associated with the peaks of contagious diseases like influenza, i.e., July-September 11, 15, 16 .
• Even in a country like India with plenty of sunshine, vitamin D deficiency is common due to reduced skin exposure and specific dietary habits such as vegetarianism 27 .
• In light of this emerging evidence regarding vitamin D and COVID-19, the authors aim to explore the role of monsoon season as well as how it potentially decreases the protective role of UVB in reducing COVID-19 deaths by reducing the likelihood of exposure to UVB radiation.

3.1 Description of Data

• In order to identify the relation of monsoon season, UVI and their interaction with COVID-19 deaths, the authors constructed the dataset outlined in Table 1 . 34 of these administrative regions reported more than 20 COVID-19 infections on 8 August 2020.
• Furthermore, the authors drop the first 20 daily observations of every administrative region after the reporting of the first COVID-19 infection in respective regions.
• Thus, the authors ensure that these observations at the very early stage of the outbreak do not bias the results.
• They also consist of the time of arrival of monsoon season for each administrative region, the daily ultraviolet index (UVI), an indicator of daily UVB radiation, as well as a set of daily weather parameters.
• Net based on the latitude and longitude information of countries that are provided by Geocoder, a geocoding library in Python.

3.2 Description of Methodology

• The authors model aims to isolate all weather parameters from region-specific time-constant factors.
• The Mundlak model combines the robustness of a fixed-effects model and the efficiency of a random-effects model.
• Instead of demeaning the structural model to isolate the weather parameters analytically from such region-specific time-constant factors, it models those region-specific time-constant factors through the available weather parameters.
• The authors describe their methodology and how to interpret the estimated associations in more detail in Supplementary Material section 1 and section 2.

4 Results

• The copyright holder for this this version posted September 25, 2020.
• The robustness checks in Table S1 (Supplementary Material) outline that their estimations are consistent when using more flexible time trends as well as to the impact of governmental measures on the behaviour of individuals.

5 Discussion

• The authors also acknowledge that the results of their study cannot serve as health guidance for India.
• The authors hope their results prompt further clinical research in India specifically to establish the role of sensible sunlight exposure or vitamin D in mitigating COVID-19 deaths during monsoon season.
• Establishing the effectiveness of sensible solar UVB exposure or vitamin D supplementation could substantially advance the control of COVID-19 pandemic at scale in India.
• The results of these clinical studies can further guide policy decision making in India, especially during monsoon season.
• This type of policy intervention would be desirable for India not only due to its lower risk and costs, but also due to its scalability across India's 1.3 billion people whose economic means vary significantly.

8 Author Contributions

• RKM conceptualized the research idea, conducted literature research, designed theoretical framework and collected COVID-19 and weather data.
• LK designed empirical methods and analyzed the data.
• RKM and LK interpreted the results and wrote the article.

Figures

Table 2: Descriptive statistics of data set

Table 1: Summary of dataset

Table 3: Effect of Monsoon Season, UVI and their interaction on cumulative COVID-19 deaths

Full text

1
Implications of Monsoon Season
& UVB Radiation
for COVID-19 in India
Manuscript
Rahul Kalippurayil Moozhipurath*
1
, Lennart Kraft
1
(Faculty of Economics and Business, Goethe University Frankfurt
1
)
Rahul Kalippurayil Moozhipurath; Lennart Kraft; Faculty of Economics and Business, Goethe
University Frankfurt, Theodor-W.-Adorno-Platz 4, 60629 Frankfurt, Germany; email:
rahulkm85@gmail.com, Phone: +49-152-1301-0589; email: lennart.kraft@wiwi.uni-frankfurt.de;
Phone +49-69-798-34769;
All rights reserved. No reuse allowed without permission.
perpetuity.
preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in
The copyright holder for thisthis version posted September 25, 2020. ; https://doi.org/10.1101/2020.09.24.20200576doi: medRxiv preprint
NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.

2
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.
All rights reserved. No reuse allowed without permission.
perpetuity.
preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in
The copyright holder for thisthis version posted September 25, 2020. ; https://doi.org/10.1101/2020.09.24.20200576doi: medRxiv preprint

3
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.
All rights reserved. No reuse allowed without permission.
perpetuity.
preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in
The copyright holder for thisthis version posted September 25, 2020. ; https://doi.org/10.1101/2020.09.24.20200576doi: medRxiv preprint

4
1 Introduction
COVID-19 has caused unparalleled economic and health disruptions in India, the second
most populated country with over 1.3 billion people. As of September 2, India has reported
66,333 COVID-19 deaths across 36 administrative regions, placing India third in the world
behind the US and Brazil
1
.
Recent observational and clinical studies show that vitamin D deficiency might be linked
to incidence
2,3
, severity
4
5
and mortality
6–8
associated with COVID-19. Recent studies show
that vitamin D and its primary source Ultraviolet-B radiation (UVB) may play a protective
role in mitigating COVID-19 deaths
9,10
. Studies indicate that south-west monsoon season
(monsoon season) plays a role in the dynamics of contagious diseases, which tend to peak
post-monsoon season
11
. The respective roles of the monsoon season and UVB in COVID-19
in India are still unclear. We anticipate a sudden increase in contagious diseases during and
post monsoon season, which will stress India’s healthcare system
12,13
. Limited hours of
sunlight and dense cloud cover
14
limit the intensity of UVB radiation, mitigating its protective
role
9
during the monsoon season. Even though limited outdoor activities during the monsoon
season may decrease the likelihood of transmission; we anticipate that it may also lead to a
lower likelihood of UVB exposure, further mitigating its protective role. To the best of our
knowledge, so far, no empirical study has explored the roles of the monsoon season and UVB
in COVID-19 in India, specifically studying the association between monsoon season, the
subsequent reduced exposure likelihood of UVB radiation and COVID-19 deaths in India.
In this observational study, we empirically describe the roles of the monsoon season and
further explore, whether monsoon season result in a reduction in the protective role of UVB in
COVID-19 deaths in India. After controlling for various confounding factors, we observe that
in the long run the monsoon season and a unit increase in UVI are separately associated with
12.8 percentage points [p<0.05] and 2.0 percentage points [p<0.05] decline in COVID-19
All rights reserved. No reuse allowed without permission.
perpetuity.
preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in
The copyright holder for thisthis version posted September 25, 2020. ; https://doi.org/10.1101/2020.09.24.20200576doi: medRxiv preprint

5
deaths growth rate. On the other hand, in the long run the monsoon season reduces the
protective role of UVI by 1.3 percentage points [p<0.05], plausibly due to lower UVB
exposure. Consequently, it is expected that although the monsoon season is helping mitigate
the transmission of Covid-19, it is doing so at the cost of UVB exposure.
2 Impact of Monsoon on Healthcare System, UVB
Radiation & COVID-19 Deaths in India
Studies indicate that the monsoon season and post-monsoon season may be associated
with the peaks of contagious diseases like influenza, i.e., July-September
11,15,16
. Heavy rainfall
linked to monsoon season may create situations favourable for the outbreaks of infectious
diseases such as diarrheal disease, cholera, dengue, typhoid as well as respiratory diseases
17
.
Furthermore, the temporal overlap between these contagious diseases and COVID-19 may
give rise to significant health care challenges
12
. The consequences of possible coinfection
with these infectious diseases and SARS-CoV-2 are largely unknown
12,13
. Moreover, we
anticipate this sudden increase in contagious diseases during monsoon season to create stress
in the healthcare system, further restricting the hospital capacity required for COVID-19
patients
12,13
. Heavy precipitation may also cause disruptions in traffic, limiting the
transportation possibilities of COVID-19 patients
13
. On the other hand, the monsoon season
also plays a protective role due to restricted mobility
18
as people are more likely to stay
indoors, reducing the possibility of the transmission of the virus. In general, the impact of the
monsoon season on COVID-19 in India remains largely unknown.
In addition to the above consequences in the healthcare system, another important
consequence of the monsoon season is the higher precipitation and the reduced likelihood of
UVB exposure and subsequently lower vitamin D levels
19
. Studies indicate that UV radiation
inactivates viruses in fomite transmission
20
. UVB also plays another protective role via its
role in vitamin D skin synthesis
21–25
, as dietary intake (natural food, fortified food or
All rights reserved. No reuse allowed without permission.
perpetuity.
preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in
The copyright holder for thisthis version posted September 25, 2020. ; https://doi.org/10.1101/2020.09.24.20200576doi: medRxiv preprint

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Implications of monsoon season & uvb radiation for covid-19 in india manuscript" ?

Preprint ( which was not certified by peer review ) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 25, 2020. 

Q2. What is the role of UVB in reducing COVID-19 deaths?

Sensible sunlight exposure9 is crucial as disproportionate solar UV exposure leads to health hazards such as aging44, wrinkles44, sunburn26 and DNA damage44. 

Q3. How many days did the authors collect COVID-19 data?

The authors collected COVID-19 data across 36 administrative regions (28 states and 8 union territories) of India covering 148 days from 14 March 2020 until 8 August 2020. 

Q4. What is the effect of monsoon season on UVI?

In the long run, Indian monsoon season further reduces the protective role of UVI by 1.3 percentage points, potentially due to lower UVB exposure as a result of decreased outdoor activities. 

Q5. What is the effect of the UVI index on COVID-19 deaths?

Apermanent unit increase of UVI is associated with a decline in COVID-19 growth rates of 37% (= −0.02/0.054) as relative to the average daily growth rates of COVID-19 deaths. 

Q6. What is the effect of the monsoon season on COVID-19 deaths?

monsoon season mitigates the association of UVI by 1.3 percentage points [p<0.05] and thus alleviates the protective role of UVI. 

Q7. How does the model estimate COVID-19 deaths?

Within two weeks of the arrival, monsoon season is associated with a reduction of COVID-19 growth rates of 59% (= −0.128 ∙ 1456 /0.054) relative to the average daily growth rates of COVID-19 deaths. 

Q8. How does the model interpret COVID-19 deaths?

A permanent unit increase of UVI is associated with a decline of 2 percentage points [p<0.05] in daily growth rates of COVID-19 deaths. 

Q9. What are the main variables used to determine the effect of COVID-19?

The authors use these weather parameters as control variables, and these parameters include cloud index, ozone level, visibility level, humidity level, minimum and maximum temperature. 

Q10. How many days of the year are the dummy variables used?

The authors include 56 days moving average of the monsoon season dummy variables, which indicate whether the monsoon season has been active in a region on a specific day.