1Department of Zoology, Asutosh College (University of Calcutta), Kolkata, India 2Department of Zoology, Asutosh College (University of Calcutta), Kolkata,India 3Department of Community Medicine, Armed Forces Medical College, Pune, Maharashtra, India *Corresponding author email: sajal_58@rediffmaill.com The COVID-19 pandemic caused by a zoonotic virus - Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) demands knowledge about the impact of environmental factors in the epidemiology of the disease. Lower air temperature and lower humidity could be associated with increased SARS-CoV-2 transmission like other human coronaviruses (HCoVs). The higher stability of SARS-CoV-2 in lower temperature is also reinforcing this assumption. In winter, the levels of atmospheric particulate matter (PM) remains significantly high which could act as a mechanical transport vector for SARS- CoV-2 apart from its role as a pollutant that causes inflammation in the lungs and contribute to the severity of COVID-19. Moreover, inhaling small airborne droplets is also a probable transmission route for SARS-CoV-2 and this could be significant during longer indoor staying behavior in winter. Asymptomatic and pre-symptomatic cases of SARS-CoV-2 are also evident. High population density in urban areas forces more people to share common space inside houses, thus creating a possible virogenic environment. It is postulated that the changes in human behavior, such as staying relatively more time indoors, and the increased stability of SARS-CoV-2 during the winter months along with higher atmospheric PM concentration may develop a favorable situation for SARS-CoV-2 transmission. Keywords: SARS-CoV-2; Atmospheric Particulate Matter; Indoor Staying Behavior; Transmission Dynamics Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causing COVID-19 disease has led to over 1.5 million deaths with more than 65 million confirmed cases around 220 countries since its emergence in Wuhan, China (WHO, 2020). Emergences of more evolved SARS-CoV-2 strains are possible and this could complicate the situation further (Chatterjee and Bhattacharya, 2020). The novelty of the virus demands knowledge about the impacts of environmental factors on its transmission dynamics (Bhattacharya et al., 2020). Studies showed that in favorable climatic conditions air pollutants - such as particulate matter (PM) - could function as mechanical transporter of SARS-CoV-2, and likely facilitate the longevity of the virus (Martelletti and Martelletti, 2020; Conticini et al., 2020 & Frontera et al., 2020). Atmospheric PM (PM 2.5 and PM 10) level varies in different season and has been found to be the highest in winter (Vinitketkumnuen et al., 2002). Lower air temperature and lower humidity can be associated with increased SARS-CoV-2 transmission (Chin et al., 2020). Shortened half-life of SARS-CoV-2 at warmer temperatures and higher humidity (Chin et al., 2020) along with the seasonality of other HCoVs such as HCoV-NL63 (Abdul-Rasool and Fielding, 2010), HCoV-HKU1 (Esper et al., 2006), and flu viruses (Sooryanarain and Elankumaran, 2015) are indicative and reinforcing this assumption. Primarily seasonal coronaviruses (sCoVs) causing common cough and cold (viz. HCoV-229E, HCoV-OC43, HCoV-HKU1, and HCoV-NL63) in most temperate sites are found to be prevalent in winter months (Li et al., 2020). In tropical countries, in winter people prefer to stay more indoors to be protected from the cold outside, thereby, increasing the possibilities of exposure to the infection in a confined indoor environment (Comunian et al. 2020 & WHO, 2020). This review will explore the possible association between PM levels in different seasons and SARS-CoV-2 transmission. Attempt has also been made to assess and analyze the impact of indoor staying behavior in winter on the transmission of SARS-CoV-2. Atmospheric PM is a heterogeneous mixture of solid and liquid particles suspended in the air with various sizes and chemical compositions (WHO, 2013). Domestic coal burning in stoves, used for winter domestic heating, and vehicular traffic are the key sources of PM (Jandacka and Durcanska, 2019). Being trapped in the nose, mouth, or throat PM can easily go through the lung and be absorbed in the blood circulation system (Dobaradaran et al., 2016 & Marzouni et al., 2017). It has been reported that atmospheric PM could act as a mechanical transport vector and carry viruses (Comunian et al., 2020). SARS- CoV-2 could also get transmitted through air, where atmospheric PM can function as a carrier through the aerosol and in turn enhances the spread of the virus (Comunian et al., 2020). Moreover, PM induces inflammation in lung cells, thus exposure to PM could intensify the susceptibility and severity of COVID-19. Angiotensin-converting enzymes 2(ACE2) receptor produces anti-inflammatory peptides and remains over-expressed during inflammation from the PM exposure. This over-expression can increase the probability of SARS-CoV-2 to penetrate the cells as the virus needs to bind with the ACE2 receptor to enter the cell (Comunian et al., 2020 & Lin et al., 2018). Several scientists demonstrated seasonal patterns in PM 2.5 concentrations which remain highest during the winters followed by pre-monsoon, post-monsoon, and monsoon seasons, and PM10 which also remains much higher in winters as compared to the other seasons (Vinitketkumnuen et al., 2002; Devraj et al., 2019). The higher PM levels in urban areas in winter are significant in the context of SARS-CoV-2 transmission as a positive correlation has been drawn by investigators between the case incidences and atmospheric PM concentrations (Zhu et al., 2020). Moreover, during the 2003 SARS outbreak in China, a positive association was also seen between the SARS case-fatality rate and pollution measures (Cui et al., 2003). The likely airborne transmission of SARS-CoV-2 by the dissemination of aerosol, like many respiratory viruses, particularly in indoor settings with poor ventilation has been deliberated and discussed by many authors (WHO, 2020; Kohanski et al., 2020; Comunian et al., 2020). In a room setting, emission of moist droplets from mouth and nose are influenced by the initial velocity of release. These droplets begin to evaporate, their size decreases, and eventually become small enough to re- circulate in the air (Kohanski et al., 2020; Comunian et al., 2020). People prefer to stay indoors in winter with the windows and doors closed most of the time. Comparison between developed countries and developing countries shows that the population density in urban areas is much higher in the developing countries and a significant percentage of people live in slums as well (World Bank, 2020 a, b). This suggests that the number of people sharing common space inside houses in these areas is more than usual, which thus brings more people together in close contact in poorly ventilated settings. It has been perceived in experimental studies that air re-circulation in public transports such as buses can increase the risk of SARS-CoV-2 infection owing to its possible airborne transmission mechanism (Shen et al., 2020). In urban and suburban areas of developing countries, most people do not have private transport, which forces them to avail public transportations. These vehicles having several people inside and the windows closed in winter create a propitious situation for viral transmission through airborne pathways, inevitably increasing the chances of viral infection. HCoV-OC43, -229E, -NL63, and -HKU1 that causes upper and lower respiratory tract infections (Bhattacharya et al., 2020) are known for their seasonal prevalence. Studies revealed that these coronaviruses are up to 10 folds more prevalent during the winter months in comparison to summers (Neher et al., 2020). A similar pattern has been observed for the SARS-CoV, as the virus was most prevalent and had peak transmission at a mean temperature of 16.9˚C with mean relative humidity of 52.2% (Yuan et al., 2006). The community transmission of SARS coronavirus during the 2003 epidemic in the subtropical cool environment can be attributed to its better stability at low temperature and low humidity (Chan et al., 2011). The role of temperature and humidity in the stability of SARS-CoV-2 has also been demonstrated by several groups of investigators (Biryukov et al., 2020; Chin et al., 2020). Experimental results provide evidence that SARS-CoV-2 decayed more rapidly when either humidity or temperature was increased (Biryukov et al., 2020; Chin et al., 2020; Bhattacharya et al., 2020). Chin et al., 2020 reported that SARS-CoV-2 is highly stable at 4˚C with a log-unit reduction of 0.7 after 14 days of incubation and when the temperature was increased to 70˚C the time for inactivation reduced only to 5 minutes. Furthermore, the half-life of SARS-CoV-2 at room temperature (24°C), ranges from 6.3 to 18.6 hours depending on the relative humidity (Biryukov et al., 2020) with the half-life in aerosol being approximately about 1.1-1.2 hours (Zhu et al., 2020). During the winters the ultraviolet radiation from direct sunlight is much less (Thieden et al., 2006) in comparison to summer. This in turn may increase the prevalence of SARS-CoV-2, especially in aerosol, as experimentally UV radiation has been found to be effective in inactivating SARS-CoV-2 (Ratnesar-Shumate et al., 2020). The significance of viral transmission via aerosol has been profoundly discussed in respect of the SARS-CoV-2 transmission dynamics. Several investigators apprehended possible links between air pollution and the transmission of SARS-CoV-2, owing to the ability of atmospheric PM to act as a mechanical carrier of SARS-CoV-2 (Setti et al., 2020; Conticini et al., 2020; Brandt et al., 2020). Pollution-induced inflammation has also been considered as a putative factor to increase the severity and symptoms of SARS-CoV-2 infection (Comunian et al., 2020). The Italian regions Lombardy and Emilia Romagna, with the highest air pollutions level, were the focused points of the SARS-CoV-2 outbreak in Italy and recorded the highest SARS- CoV-2 lethality (Conticini et al., 2020). Furthermore, a significant positive correlation has been found between morbidity and mortality of COVID-19 and high pollution levels in cities of China’s Hubei province, the epicenter of the SARS-CoV-2 outbreak (Brandt et al., 2020). Comparative analysis of PM concentrations at different months also validates the fact that PM concentration in the air remains significantly higher in the winter season (Vinitketkumnuen et al., 2002; Devraj et al., 2019). Considering this association between winter and high PM concentration possibilities arise that SARS-CoV-2 transmission can be facilitated in winter by the increased atmospheric PM concentrations. Similar associations of higher prevalence of influenza virus in winter due to higher atmospheric PM have been made by many investigators (Liang et al., 2014; Murtas and Russo, 2019). However, this assumption requires further validation through experimental studies and field evidences. It has been found that sharing indoor space could be a major risk factor in the transmission of SARS‐CoV‐2 (Allen and Marr, 2020) and could be ascribed to the airborne transmission of the virus. Apart from the widely recognized transmission via larger respiratory droplets and direct contact, inhaling small airborne droplets is also a probable transmission route for SARS-CoV-2 (Morawska et al., 2020; WHO, 2020). During the winters this mode of transmission can be more significant due to the prolonged indoor stay of humans by compulsion. Moreover, high population density with a significant percentage of slum living people (World Bank, 2020b) in urban areas of developing countries could also increase the risk of infection. High population density indicates more number of people sharing a single household or living space, which in turn may create a congenial situation for the establishment of a virogenic environment during the winters. The higher case incidences of COVID-19 in urban areas of India than in rural areas could also be attributed to the population density (V et al., 2020). Furthermore, the stability of SARS-CoV-2 for extended periods on surfaces under indoor conditions has been well demonstrated (Ratnesar-Shumate et al., 2020). Transmission of SARS-CoV-2 from asymptomatic and pre-symptomatic persons has been reported, but to what extent and the transmission routes are not yet fully understood (Gao et al., 2020). During the winters, common cold or influenza are commonly prevalent with symptoms like sneezing and coughing (Acharya and Thapa, 2016). Co-infection of patients with both influenza and SARS-CoV-2 has been found (Konala et al., 2020). Owing to longer indoor stay in winter, the pre-symptomatic and asymptomatic persons if any could also unknowingly transmit the virus to others. The possibility of SARS-CoV-2 transmission from asymptomatic and pre-symptomatic individuals during indoor staying is a matter of great concern, hence requires a comprehensive scientific investigation in order to formulate the preventive strategies. Airborne transmission risk also gets influenced by aerosol properties, virus‐specific, and host‐specific factors (Kohanski et al., 2020) which are beyond the scope of this review. During the winters, people tend to stay more indoors, and hence deprive themselves of reasonable sunlight, which may lead to vitamin D deficiency. This deficiency may weaken the immune system (Acharya and Thapa, 2016). Prevalence of several respiratory diseases such as influenza, tuberculosis, cystic fibrosis has been linked with Vitamin D deficiecy and compromised immunity (Hughes and Norton, 2009; Acharya and Thapa, 2016). A similar association has been reported between the COVID-19 and Vitamin D as well (Marik et al., 2020; Grant et al., 2020; Radujkovic et al., 2020). Almost all of the HCoVs are prevalent during the winters owing to their high stability at low temperature and humidity (Biryukov et al., 2020; Chin et al., 2020) in different bio-geographical regions. It is postulated that the changes in human behavior, such as staying relatively more time indoors, and the increased stability of SARS-CoV-2 in winter along with higher atmospheric PM concentration may create a congenial environment for SARS-CoV- 2 transmission. The seasonality of HCoVs including the SARS-CoV is a known phenomenon for many years. However, the seasonal prevalence of the novel coronavirus (SARS-CoV-2) is not yet evidenced. In winter, the PM remains closer to the surface with higher concentrations than usual. This situation prevails especially in urban areas. The increased PM concentration favors SARS-CoV-2 transmission. Atmospheric PM not only causes lung infections but also amplifies the severity of COVID-19 and enhances the possible transmission of the virus through aerosols. The airborne transmission has been evidenced during previous coronavirus epidemics (SARS-CoV and MERS-CoV). Airborne transmission by dissemination of aerosol is proposed as a route of SARS-CoV-2 transmission, especially in poorly ventilated settings. Indoor staying behavior in winter forces people to be in closed and poorly ventilated environments which create conducive situations for disease transmission. The spread of human coronaviruses is more serious in urban areas, and the higher population density could be one of the reasons behind this. Nevertheless, the magnitude of COVID-19 cases may vary even in winter months in different regions of the world as the above-mentioned factors are not the only drivers of the disease. We conclude that in winter, higher PM concentrations and increased indoor staying behavior, specially in urban areas, could create a transmission-friendly situation for SARS-COV-2 and can contribute as important drivers in the COVID-19 disease epidemiology. The authors declare that they have no conflict of interest. The first three authors (SB, SS, TG) render their sincere gratitude towards Professor A. Roy, Vice Principal, Asutosh College, Kolkata, and Dr. S. Dutta Roy Head, Postgraduate Department of Zoology, Asutosh College, Kolkata for their kind support during the work. Abdul-Rasool, S. & Fielding, B. C. (2010). Understanding Human Coronavirus HCoV-NL63. The Open Virology Journal, 4, pp:76–84. Acharya, B. & Thapa, K. (2016). Indoor Staying During Winter Season Makes People More Susceptible to Flu. Journal of Nepal Health Research Council, 14(32), pp:69–70. Allen, J. G. & Marr, L. C. (2020). Recognizing and controlling airborne transmission of SARS-CoV-2 in indoor environments. Indoor Air, 30(4), pp:557–558. Bhattacharya, S., Sinha S., Baidya, D. & Tilak, R. (2020) Emergence of a Zoonotic Pathogen - Novel Coronavirus (SARS- CoV-2) in the Context of Changing Environment. Journal of Communicable Diseases, 52(2), pp:67-73. Bhattacharya, S., Sinha, S., Tilak, R. & Mardihusodo, S.J. The relationship between bats and human coronavirus: An exploratory review. Journal of Health and Social Science. 2020;5(2) pp:219-230 Biryukov, J., Boydston, J. A., Dunning, R. A., Yeager, J. J., Wood, S., Reese, A. L., Ferris, A., Miller, D., Weaver, W., Zeitouni, N. E., Phillips, A., Freeburger, D., Hooper, I., Ratnesar-Shumate, S., Yolitz, J., Krause, M., Williams, G., Dawson, D. G., Herzog, A., Dabisch, P. & ltamura, L. A. (2020). Increasing Temperature and Relative Humidity Accelerates Inactivation of SARS-CoV-2 on Surfaces. mSphere, 5(4), pp: e00441-20. Brandt, E. B., Beck, A. F. & Mersha, T. B. (2020). Air pollution, racial disparities, and COVID-19 mortality. The Journal of Allergy and Clinical Immunology, 146(1), pp: 61–63. Chan, K. H., Peiris, J. S., Lam, S. Y., Poon, L. L., Yuen, K. Y. & Seto, W. H. (2011). The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus. Advances in virology, pp: 734690. Chatterjee, R. & Bhattacharya, S. (2020). Could Novel Corona Virus (Sars-Cov-2) Be The Evolving Face of A New Generation of Genetically Complex Epidemiological Challenge?. Malaysian Journal of Medical Research (MJMR), 4(2), pp: 42-45. Chin, A., Chu, J., Perera, M., Hui, K., Yen, H. L., Chan, M., Peiris, M. & Poon, L. (2020). Stability of SARS-CoV-2 in different environmental conditions. The Lancet. Microbe, 1(1), pp: e10. Comunian, S., Dongo, D., Milani, C. & Palestini, P. (2020). Air Pollution and Covid-19: The Role of Particulate Matter in the Spread and Increase of Covid-19's Morbidity and Mortality. International Journal of Environmental Research and Public Health, 17(12), pp:4487. Conticini, E., Frediani, B. & Caro, D. (2020). Can atmospheric pollution be considered a co-factor in extremely high level of SARS-CoV-2 lethality in Northern Italy?. Environmental Pollution (Barking, Essex : 1987), 261, pp: 114465. Cui, Y., Zhang, Z. F., Froines, J., Zhao, J., Wang, H., Yu, S. Z. & Detels, R. (2003). Air pollution and case fatality of SARS in the People's Republic of China: an ecologic study. Environmental Health : A Global Access Science Source, 2(1), pp: 15. Devaraj, S., Tiwari, S., Ramaraju, HK., Dumka, U.C., Sateesh, M., Parmita, P. & Shivashankara, G.P.(2019) Spatial and Temporal Variation of Atmospheric Particulate Matter in Bangalore: A Technology-Intensive Region in India. Archives of Environmental Contamination and Toxicology. 77(2), pp:214-222. Dobaradaran, S., Geravandi, S., Goudarzi, G., Idani, E., Salmanzadeh, S., Soltani, F., Yari, A.R. & Mohammadi, M.J.(2016). Determination of Cardiovascular and Respiratory Diseases Caused by PM10 Exposure in Bushehr, 2013. Journal of Mazandaran University of Medical Science, 26 (139), pp: 42-52. Esper, F., Weibel, C., Ferguson, D., Landry, M. L. & Kahn, J. S. (2006). Coronavirus HKU1 infection in the United States. Emerging Infectious Diseases, 12(5), pp: 775–779. Frontera, A., Martin, C., Vlachos, K. & Sgubin, G. (2020). Regional air pollution persistence links to COVID-19 infection zoning. The Journal of Infection, 81(2), pp: 318–356. Gao, W. J. & Li, L. M. (2020). Zhonghua Liu Xing Bing Xue Za Zhi = Zhonghua Liuxingbingxue Zazhi, 41(4), pp: 485–488. Grant, W. B., Lahore, H., McDonnell, S. L., Baggerly, C. A., French, C. B., Aliano, J. L. & Bhattoa, H. P. (2020). Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients, 12(4), pp: 988. Jandacka, D. & Durcanska, D. (2019) Differentiation of Particulate Matter Sources Based on the Chemical Composition of PM10 in Functional Urban Areas. Atmosphere, 10, pp: 583. Hughes, D. A. & Norton, R. (2009). Vitamin D and respiratory health. Clinical and Experimental Immunology, 158(1), pp: 20– 25. Kohanski, M. A., Lo, L. J. & Waring, M. S. (2020). Review of indoor aerosol generation, transport, and control in the context of COVID-19. International Forum of Allergy & Rhinology, 10(10), pp: 1173–1179. Konala, V. M., Adapa, S., Gayam, V., Naramala, S., Daggubati, S. R., Kammari, C. B. & Chenna, A. (2020). Co-infection with Influenza A and COVID-19. European Journal of Case Reports In Internal Medicine, 7(5), pp: 001656. Li, Y., Wang, X. & Nair, H. (2020). Global Seasonality of Human Seasonal Coronaviruses: A Clue for Postpandemic Circulating Season of Severe Acute Respiratory Syndrome Coronavirus 2?. The Journal of Infectious Diseases, 222(7), pp: 1090–1097. Liang, Y., Fang, L., Pan, H., Zhang, K., Kan, H., Brook, J. & Sun, O. (2014) PM2.5 in Beijing - temporal pattern and its association with influenza. Environmental Health, 13, pp: 102. Lin, C. I., Tsai, C. H., Sun, Y. L., Hsieh, W. Y., Lin, Y. C., Chen, C. Y. & Lin, C. S. (2018). Instillation of particulate matter 2.5 induced acute lung injury and attenuated the injury recovery in ACE2 knockout mice. International journal of biological sciences, 14(3), pp: 253–265. Marik, P. E., Kory, P. & Varon, J. (2020). Does vitamin D status impact mortality from SARS-CoV-2 infection?. Medicine in drug discovery, 6, pp: 100041. Martelletti, L. & Martelletti, P. (2020). Air Pollution and the Novel Covid-19 Disease: a Putative Disease Risk Factor. SN comprehensive clinical medicine, 1–5. Advance online publication. https://doi.org/10.1007/s42399-020-00274-4 Marzouni, M. B., Moradi, M., Zarasvandi, A., Akbaripoor, S., Hassanvand, M. S., Neisi, A., Goudarzi, G., Mohammadi, M. J., Sheikhi, R., Kermani, M., Shirmardi, M., Naimabadi, A., Gholami, M., Mozhdehi, S. P., Esmaeili, M. & Barari, K. (2017). Health benefits of PM10 reduction in Iran. International Journal of Biometeorology, 61(8), pp: 1389–1401. Morawska, L., Tang, J. W., Bahnfleth, W., Bluyssen, P. M., Boerstra, A., Buonanno, G., Cao, J., Dancer, S., Floto, A., Franchimon, F., Haworth, C., Hogeling, J., Isaxon, C., Jimenez, J. L., Kurnitski, J., Li, Y., Loomans, M., Marks, G., Marr, L. C., Mazzarella, L. & Yao, M. (2020). How can airborne transmission of COVID-19 indoors be minimised?. Environment International, 142, pp:105832. Murtas, R. & Russo, AG. (2019) Effects of pollution, low temperature and influenza syndrome on the excess mortality risk in winter 2016-2017. BMC Public Health, 19(1), pp:1445. Neher, R. A., Dyrdak, R., Druelle, V., Hodcroft, E. B. & Albert, J. (2020). Potential impact of seasonal forcing on a SARS- CoV-2 pandemic. Swiss Medical Weekly, 150, pp: w20224. Ratnesar-Shumate, S., Williams, G., Green, B., Krause, M., Holland, B., Wood, S., Bohannon, J., Boydston, J., Freeburger, D., Hooper, I., Beck, K., Yeager, J., Altamura, L. A., Biryukov, J., Yolitz, J., Schuit, M., Wahl, V., Hevey, M. & Dabisch, P. (2020). Simulated Sunlight Rapidly Inactivates SARS-CoV-2 on Surfaces. Journal of Infectious Diseases, 222(2). Setti, L., Passarini, F., De Gennaro, G., Barbieri, P., Perrone, M. G., Borelli, M., Palmisani, J., Di Gilio, A., Torboli, V., Fontana, F., Clemente, L., Pallavicini, A., Ruscio, M., Piscitelli, P. & Miani, A. (2020). SARS-Cov-2RNA found on particulate matter of Bergamo in Northern Italy: First evidence. Environmental Research, 188, pp:109754. Shen, Y., Li, C., Dong, H., Wang, Z., Martinez, L., Sun, Z., Handel, A., Chen, Z., Chen, E., Ebell, M. H., Wang, F., Yi, B., Wang, H., Wang, X., Wang, A., Chen, B., Qi, Y., Liang, L., Li, Y., Ling, F.& Xu, G. (2020). Community Outbreak Investigation of SARS-CoV-2 Transmission Among Bus Riders in Eastern China. JAMA Internal Medicine, e205225. Advance online publication. Sooryanarain, H. & Elankumaran, S. (2015). Environmental role in influenza virus outbreaks. Annual Review of Animal Biosciences, 3, pp: 347–373. Thieden, E., Philipsen, P. A. & Wulf, H. C. (2006). Ultraviolet radiation exposure pattern in winter compared with summer based on time-stamped personal dosimeter readings. The British Journal of Dermatology, 154(1), pp: 133–138. V, A., R, V. & Haghighat, F. (2020). The contribution of dry indoor built environment on the spread of Coronavirus: Data from various Indian states. Sustainable Cities and Society, 62, pp: 102371. Vinitketkumnuen, U., Kalayanamitra, K., Chewonarin, T. & Kamens, R. (2002). Particulate matter, PM 10 & PM 2.5 levels, and airborne mutagenicity in Chiang Mai, Thailand. Mutation Research, 519(1-2), pp: 121–131. WHO (2013). Health effects of particulate matter. Policy implications for countries in eastern Europe, Caucasus and central Asia. Copenhagen: WHO Regional Office for Europe; 2013 Retrieved From: http://www.euro.who.int/ data/assets/pdf_file/0006/189051/ Health-effects-of-particulate-matter-final-Eng.pdf WHO (2020) World Health Organization, Coronavirus Disease(COVID-19) Pandemic. Retrieved From: https://www.who.int/emergencies/diseases/novel-coronavirus-2019. WHO (2020) Transmission of SARS-CoV-2: implications for infection prevention precautions. Retrieved From: https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention- precautions. World Bank (a). 2020. Population Living in Slums (% of Urban Population). World Developmental Indicators. Retrieved From: https://data.worldbank.org/indicator/EN.POP.SLUM.UR.ZS World Bank (b). 2020. Urban Population. World Developmental Indicators. Retrieved From: https://data.worldbank.org/indicator/SP.URB.TOTL Yuan, J., Yun, H., Lan, W., Wang, W., Sullivan, S. G., Jia, S. & Bittles, A.H. (2006). A climatologic investigation of the SARS- CoV outbreak in Beijing, China. American Journal of Infection Control, 34(4),pp: 234–236.ABSTRACT
INTRODUCTION
Review of Literature
Atmospheric Particulate Matter and SARS Coronaviruses
Indoor Staying Behavior in Winter and its Possible Association with SARS-CoV-2
Seasonal Prevalence of Human Coronaviruses
DISCUSSION
CONCLUSION
Conflict of Interests
ACKNOWLEDGEMENT
REFERENCES
Bhattacharya, S., Basu, P. & Poddar, S. (2020). Changing epidemiology of SARS-CoV in the context of COVID-19 pandemic. Journal of Preventive Medicine and Hygiene, 61(2), pp:130-136.
Radujkovic, A., Hippchen, T., Tiwari-Heckler, S., Dreher, S., Boxberger, M. & Merle, U. (2020). Vitamin D Deficiency and Outcome of COVID-19 Patients. Nutrients, 12(9), pp: 2757.
Zhu, Y., Xie, J., Huang, F. & Cao, L. (2020). Association between short-term exposure to air pollution and COVID-19 infection: Evidence from China. The Science of the Total Environment, 727, pp: 138704.