Relationship between Climate Variables and New Daily COVID-19 Cases in Dhaka, Bangladesh

The present study investigates the relationship between the transmission of COVID-19 infections and climate indicators in Dhaka City, Bangladesh, using coronavirus infections data available from the Institute of Epidemiology, Disease Control and Research (IEDCR), Bangladesh. The Spearman-ranked correlation test was carried out to study the association of seven climate indicators, including humidity, air quality, minimum temperature, precipitation, maximum temperature, mean temperature and wind speed with the COVID-19 outbreak in Dhaka City, Bangladesh. The study found that, among the seven indicators, only three indicators (air quality, minimum temperature and average temperature) have a significant relationship with new COVID-19 cases. The results of this paper will give health regulators and policymakers valuable information to lessen the COVID-19 infection in Dhaka and other countries around the world.


Introduction
Coronavirus is a major pathogen affecting the respiratory system of humans [1]. On December 31, 2019, an unspecified etiological outbreak from Wuhan, Hubei, China was reported to the World Health Organization (WHO) [2]. The novel virus, later named as COVID-19, spread quickly to other countries around the globe. In light of the rising danger, WHO declared COVID-19 as an international public health emergency (PHEIC) [3]. COVID-19 has already infected people in most countries around the world. As of 25 th July 2020, the incidence of COVID-19 infections reached the figure of 8 million, with more than 205 countries and regions being affected by the pandemic [4]. COVID-19 clinical trials indicate that almost all patients have trouble breathing and pneumonia [5]. Clinical diagnosis has identified that COVID-19 patients have similar indications to other coronavirus affected patients, e.g.
MERS and SARS [6]. The initial indication of COVID-19 infection is cough, fever, and short breath, and in the late stage, it can damage the kidney, cause pneumonia, and unexpected death. The vulnerability of the elderly (>80 years of age) is high, with a fatality rate of ~22% of cases infected by COVID-19 [1].
In Bangladesh, the first coronavirus cases were identified on March 8, 2020, in three young patients (two male and one female). The two male patients had returned from Italy and the female was ta family member of one of the two males [7]. Bangladesh's infections remained low until the end of March but increased steeply in April. Bangladesh cases reached 100 on April 9 and exceeded 200 cases in two days, so the time for the caseload to double was two days which later slowed to three and then five days. On June 1, 2020, the time required for the caseload in Bangladesh to double remained at five days. The spread of infection was similar to that of Italy, France, and South Korea, which resulted in WHO announcing COVID-19 a pandemic [8]. Between March 8 and June 1, 2020, there were 49,534 COVID-19 cases in Bangladesh confirmed by rt-PCR, including 672 related fatalities (CFR 1.36%) according to the IEDCR. Figure 1 shows the COVID-19 case distribution up until June 1, 2020 in Bangladesh [9]. As of June 1, 2020, the geographical distribution of confirmed reported COVID-19 cases was available on 65% of all cases (32,120 of 49,534). Of these cases, 70.3% (22,576) were from Dhaka Division, 16.7% Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 29 July 2020 doi:10.20944/preprints202007.0699.v1 conditions and density of people. Dalziel et al. [12] considered climate indicators as the best predictors because weather conditions play a significant role in the transmission of coronavirus. Researcher [11,13] has also found that climate indicators significantly affect the death rate due to pneumonia. Tosepu et al. [13] cited that the adverse weather associated with long-term changes in climate made a significant contribution to West Nile virus spreading in the US and Europe. Even though some research has looked into identifying the link between weather variables and the spread of viruses, there is limited research on the relation between them. Most of these studies focused solely on observing the correlation of temperatures, while overlooking the impact of air quality on COVID-19 dynamics. The air quality index of Bangladesh indicates that Dhaka is the most polluted city, which may affect the dynamics of COVID-19 in Bangladesh. Therefore, this work will provide expedient information to the policymaker, which can help to lower the COVID-19 infection rate.

Study Area
Dhaka

Data Collection
The computer-based data on the updates of COVID-19 status in Dhaka from the period of May 1, 2020 -May 31, 2020 were procured from the IEDCR, Bangladesh. Until April 30, there were 6,000 cases recorded in Dhaka and new cases increased steadily from May 1, 2020.The data on climate indicators and atmospheric conditions during May 2020 were collected from the Bangladesh Meteorological Department (BMD) [15]. The data consists of minimum, maximum, and average temperatures in °C, precipitation in millimetres, and humidity as a percentage. The air quality index (AQI) data was collected from Dhaka US Consulate Air Pollution: Real-time Air Quality Index (Available at http://aqicn.org/city/bangladesh/dhaka/us-consulate/).

Data analysis
The data distribution is not normal. Therefore, to analyse the data, the Spearman rank correlation (rs) test was performed to inspect the correlation between new and total infections with environmental indicators.
The coefficient is calculated using the following equation [16]:  The daily temperature changes of Dhaka in May 2020 is depicted in Figure 3. The lowest daily maximum, minimum and average temperature was 24°C, 33°C and 29°C, respectively, whereas the highest daily maximum, minimum and average temperature was 26°C, 34°C and 30°C, respectively. The average daily lowest and highest rainfall was 2mm and 20mm, respectively. The average daily minimum and maximum humidity was 47% and 98%, respectively. The average daily lowest and highest wind speed was 1 km/h and 17 km/h, respectively. The average daily minimum and maximum air quality as per the AQI was 54 and 150, respectively.  For the present study, the link between climate change indicators and the spread of COVID-19 in Dhaka is analysed. Figure 4 shows the most correlation factors on daily new infections and the total number of 19 dynamics indicates that temperature served as the key driver for the spread of the coronavirus in China [18], Indonesia [13] and the US [11]. Chen et al. [19] also highlighted that temperature influences the spread of the coronavirus. There are reports of other meteorological indicators affecting the dynamics of the novel coronavirus. It has been reported that humidity and temperature are crucial indicators, which significantly motivate the seasonal transmission of COVID-19 [20]. Similar results for China have been published by Wang [6] which show a strong link between disease propagation and climate variables, predicting that sunny weather may play a crucial role in the reduction of virus transmission. However, weather parameters affect not only the transmission of the novel virus but also mortality [21]. Poole [22] cited that environment latitude also correlates with COVID-19 pandemic. The findings of this study have been compared with a recent study [13] undertaken in Indonesia which indicated that only mean temperature significantly affected daily cases, with other variables bearing no relationship with the COVID-19 pandemic. In this study, we also found that the average temperature is linked with daily new cases in Bangladesh (rs=0.472) and that the observed relationship is higher than that found for Indonesia (rs=0.393). Unlike the Indonesian study [13], this study also considered the effect of air quality on the impact of the outbreak. We found that air quality is strongly related (rs=0.607;

Results and Discussion
p=0.001)) to total cases in Bangladesh.
In Dhaka, the fast spread of COVID-19 was due to the extremely high level of human mobility, along with the weather. Being the capital city, Dhaka is the centre of commercial, economic and cultural activities of Bangladesh. Many people from regional areas in Bangladesh travel to Dhaka to find a job and develop their financial stability. Another explanation perhaps is that Dhaka has a high population density, allowing very quick transmission of COVID-19. Dhaka has a population of 21 million growing at 3.6% per year and a density of 121,720 residents per square mile, according to census data. Most of the people are involved either in households or unauthorized work and considerable proportion work in the garment industry (approximately 800,000). Such statistics make Dhaka a perfect epicentre for infection compared to other areas of the country. Zhu et al. [23] also reported that population growth is one of the causes for the rapid transmission of COVID-19 Despite important findings on the impact of weather on the COVID-19 pandemic, some limitations remain. For example, the infection of novel coronavirus is influenced by many variables including people's mobility, immunity, hygiene and proximity, the size of gatherings, testing facilities, and health care management. Therefore, further and comprehensive research is necessary to explore data about these variables to give a clearer picture of the dynamics of COVID-19.

Conclusions
Climate indicators play an important role in determining the COVID-19 outbreak in Dhaka. This study shows a significant correlation between mean temperature, low temperature, and air quality and rapid transmission of COVID-19 infections. The outcomes of this research will provide useful information to lower the incidence rate. In particular, the significant relationship between air quality and the spread of