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Abstract. This article investigated whether the atmospheric temperature had any role in the spread and vulnerability to COVID-19 worldwide and how that knowledge can be utilized to contain the fast-spreading disease. It highlighted that temperature was an important factor in transmitting the virus, and a moderately cool environment was the most favourable state for its susceptibility. In fact, the risk from the virus is reduced significantly in high temperature environment. Warm countries and places were likely to be less vulnerable. We identified various degrees of vulnerability based on temperature and specified countries for March and April. The maximum reported case, as well as death, was noted when the temperature was in the range of around 275°K (2°C) to 290°K (17°C). Countries like the USA, UK, Italy and Spain belonged to this category. The vulnerability was moderate when the temperature was less than around 275° K (2° C) and countries in that category were Russia, parts of Canada and few Scandinavian countries. For temperature 300° K (27° C) and above, a significantly lesser degree of vulnerability was noted. Countries from SAARC, South East Asia, the African continent and Australia fell in that category. In fact, when the temperature was more than 305° K (32° C), there was a unusually low number of reported cases and deaths. For warm countries, further analyses on the degree of vulnerability were conducted for the group of countries from SAARC and South East Asia and individual countries were compared. We also showed countries can switch from one vulnerability state to another based on the variability of temperature. We provided maps of temperature to identify countries of different vulnerability states in different months of the year.That influence of temperature on the virus and previous results of clinical trials with similar viruses gave us a useful insight that regulating the level of temperature can provide remarkable results to arrest and stop the outbreak. Based on that knowledge, some urgent solutions are proposed, which are practically without side effects and very cost-effective too.Introduction:The recent pandemic of COronaVIrus Disease 2019 (COVID-19) and its rapid spread worldwide1,2 brought the whole human civilization to a standstill. The responsible virus for the disease is Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS -CoV -2 ) 3. Detailed analysis of the characteristics of the virus and the nature of the disease is outlined in current research4, 5.The disease first originated in the Wuhan Province of China. The case of hospital admission was first reported on 12th December 2019 and since then till 15th March there were 80,995 reported cases in China with 3,203 confirmed deaths2. Various analyses on the COVID-19 spread in China were detailed in a recent study6. That figure all over the globe reached 1,000,249 and 51,515 respectively2 on 3rd April 2020, since 31 December 2019. Geographic distribution of COVID-19 cases worldwide are presented in Fig.1a. Because of the highly contagious in nature 3,7, most of the countries worldwide started lockdown situation from around third week of March8.Several facts highlighted that the spread of recent Coronavirus pandemic showed some geographical preferences (Fig.1). Countries and cities with moderately cold winter temperature indicated a rapid spread (UK, Italy, Spain, northern USA etc.) compared to warm countries (e.g., countries from the African continent, Indian subcontinent and, Australia)1,2. Moreover, very cold countries like Canada, Russia and Scandinavian countries only showed moderate severity. Interestingly, the countries that suggested moderate severity started showing the sign of more severity from the end of April. More importantly, it is happening in spite of a global lockdown situation. Over the same time, some warm countries (e.g, Brazil, Chilli) also suggested a rise in severity1,2.On a regional basis, compared to warmer places, colder regions were seen more affected. During February and January 2020, a sub-zero minimum temperature was noted in the Wuhan province of China where the outbreak was reported first. Wuhan experienced maximum severity in terms of the death toll and the rapid rise of infected patients. In February this year, the following cities (Rome in Italy, Tehran in Iran, Seoul in South Korea) all experienced a sub-zero minimum temperature and coincidentally showed a sharp increase in the number of infected patients. Those cities were the epicentres of the outbreak of respective countries. The numbers of infected people in Italy, Iran, South Korea are reported to be 115242, 50468 and 10062 (as of 3rdApril 2020 since 31 December 2019) 2.Close connections between epidemics and seasons are previously identified for mid-latitude temperate regions; which is November till March in the Northern Hemisphere, while May upto September in the Southern Hemisphere 9,10,11. In temperate regions, absolute humidity minimizes in winter alongside temperature which becomes more susceptible to certain virus transmission and survival10.A laboratory study using a seasonally dependent endemic virus that has close resemblance with Coronavirus also confirmed the dependence of temperature and humidity on the spread of disease11. It showed that at a temperature of 5 ºC and relative humidity (RH) 35% to 50% the infection rate was very high (75-100%). Whereas, when the RH was still kept at 35%, but only temperature was increased to 30°C the infection rate surprisingly reduced to zero11. As the infection rate was reduced to zero at temperature 30 °C and humidity 35% that estimation may be useful for arresting spread of similar viruses and needs further exploration.Another virus named the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) that share genetic similarity with COVID-19 was shown to remain active for a long time in low humidity and low temperature12. Studies with a different Coronavirus SARS-CoV (Severe Acute Respiratory Syndrome Coronavirus) also noted the same connection 13,14,15. MERS-CoV and SARS-CoV both belong to the Coronavirus genus in the Coronaviridae family16.Research also studied strength and activity for a similar generic Coronavirus (viz. SARS-CoV) using a variable level of temperature and humidity14. It found that inactivation of the virus was faster at all humidity level if the temperature was simply raised to 20°C from 4°C. Also, the inactivation was more rapid if the temperature was further increased to 40°C from 20°C, suggesting the virus is extremely sensitive to high temperature . SARS could, however, be active for at least five days in typical airconditioned environments which has relative humidity 40-50 % and room temperature 22 -25°C13. The strength of the virus was lost rapidly when relative humidity was >95% and temperatures were 38°C or higher13. Studies with various Coronavirus generic categories other than MERS and SARS also confirmed that low temperature significantly contributes to the survival and transmission of the virus14,17.COVID-19 is an extremely contagious disease 3,7 as it invaded almost all parts of the globe in less than two months1,2. The nature of its transmission under variable temperature condition also needs attention. A lab experiment was conducted using guinea pigs to examine the contamination of a similar seasonal air-borne virus11. It studied the effect of temperature on airborne transmission as well as contact transmission. Increasing the temperature prevented airborne transmission but could not stop contact transmission. When guinea pigs were kept in separate cages for 1 week at a temperature of 30°C, no infection took place among recipient guinea pigs. But to simulate contact transmission, if those were kept in the same cage, between 75% and 100% became infected. They, however, found no role of humidity in these experiments.Though the knowledge of temperature sensitivity to the similar seasonal virus is recognised, whether any early warning systems can be proposed on various space and time scales is yet to be determined18. The role of weather on the spread of COVID-19 was also studied in various analyses. Research confirmed dependencies on temperature and humidity 14,15 ; wind speed and surface pressure19 for the spread of virus. A systematic review to understand the effect of temperature on COVID-19 was also conducted21 . It collected numerous recent journal submissions (around 16 in number) and almost all of them indicated a strong dependence on temperature. There are potential that the knowledge of such analyses can be used for the benefit of human society in the current emergency situation. The role of global temperature on the transmission of COVID-19 worldwide was mentioned first by the author in a recent work 22. That knowledge was further elaborated in a subsequent study by presenting a global temperature spatial map and comparing with vulnerability worldwide23. The current analysis is an extension work to investigate that effect further. It also identifies countries that are more vulnerable/ favourable than others in various seasons.It is an extremely contagious disease3,7 and has very high epidemic potential. Scientists from different fields are working tirelessly to mitigate the crisis. Clinical trials and laboratory experiments are time consuming. Lockdown and social distancing can be a temporary solution, as the economy and mental health also need attention. With those emergency situations in mind, some effective solutions are proposed. These additional measures, apart from existing guidelines 3,7 , can greatly benefit to overcome the crisis.This article is based on the idea whether the variable global temperature has any role in the transmission of virus globally and to arrest the rapidly spreading disease, how that knowledge can be used.Methodology and Data:We analysed global air temperature data from NCEP/NCAR Reanalysis product24, a joint product from the National Center for Atmospheric Research (NCAR) and National Centers for Environmental Prediction (NCEP). The data is freely available25. It has a temporal coverage of Monthly as well as Daily values from 1948 January till recent dates. The long-term monthly mean of this data is available and derived for years 1981 - 2010. The spatial coverages extend all over the globe and has 17 vertical levels. In this analysis, we only considered the lowest level near the surface which is 1000mb. For air temperature, we calculated climatology (30 years average), as well as some daily composites using compositing technique. We also used the Method of Mean Differences to analyse the result and to find differences between two sets of data. The level of statistical significance was derived using the student’s t-test. Data related to COVID-19 are freely available and all listed underneath.