key: cord-0948803-yw0nk7fo authors: Vantarakis, A.; Chatziprodromidou, I.; Apostolou, T. title: COVID-19 and Environmental factors. A PRISMA-compliant systematic review date: 2020-05-15 journal: nan DOI: 10.1101/2020.05.10.20069732 sha: cffd81d18a1a1a0e982ff33b63085dc02edc17d7 doc_id: 948803 cord_uid: yw0nk7fo The emergence of a novel human coronavirus, SARS-CoV-2, has become a global health concern causing severe respiratory tract infections in humans. Human-to-human transmissions have been described with incubation times between 2-10 days, facilitating its airborne spread via droplets. The impact of environmental factors on the coronavirus disease 2019 (COVID-19) outbreak is under consideration. We therefore reviewed the literature on all available information about the impact of environmental factors on human coronaviruses. Temperature, humidity and other environmental factors have been recorded as environmental drivers of the COVID-19 outbreak in China and in other countries. Higher temperatures might be positive to decrease the COVID-19 incidence. In our review, the analysis of 23 studies show evidence that high temperature and high humidity reduce the COVID-19 transmission. However, further studies concerning other environmental (namely meteorological) factors role should be conducted in order to further prove this correlation. As no specific therapies are available for SARS-CoV-2, early containment and prevention of further spread will be crucial to stop the ongoing outbreak and to control this novel infectious thread. A novel coronavirus (SARS-CoV-2) has recently emerged from China with a total of 45171 confirmed cases of pneumonia (as of February 12, 2020). Coronaviruses (CoVs) most commonly cause mild illness; but have occasionally, in recent years, led to major outbreaks of human disease. Approximately ten years after SARS, another novel, highly pathogenic CoV, in December 2019, SARS-CoV-2, a novel CoV, was identified in the City of Wuhan, Hubei Province, a major transport hub of central China. The earliest COVID-19 cases were linked to a large seafood market in Wuhan, initially suggesting a direct food source transmission pathway this is the third highly pathogenic human coronavirus that has emerged in the last two decades. In the months since the identification of the initial cases, COVID-19 has spread to 180 countries and territories and there are approximately 664,564 confirmed cases and 30,890 deaths (as of 29 March 2020). Person-to-person transmission was confirmed as one of the main mechanisms of COVID-19 spread (Chan et al. 2020) . The modes of transmission have been identified as host-to-human and human-to-human. Increased spread of SARS-CoV-2 causing COVID-19 infections worldwide has brought increased attention and fears surrounding the prevention and control of SAR-CoV-2 from both the scientific community and the general public. While many of the precautions typical for halting the spread of respiratory viruses are being implemented, other less understood transmission pathways should also be considered and addressed to reduce further spread. The role of environment and its mediated pathways for infection by other pathogens have been a concern for decades. Substantial research into the presence, abundance, diversity, function, survival and transmission of microorganisms in the environment has taken place in recent years. There is preliminary evidence that environmentally mediated transmission may be possible; additionally, that COVID-2 could be affected by environmental factors such as seasonality, 4 temperature, humidity (Tan et al. 2005) (Shaman and Kohn 2009) (Geller, Varbanov, and Duval 2012) . The aim of the review was, therefore, to summarize all available data on the impact of environmental factors on the survival of all coronaviruses including emerging SARS-CoV and MERS CoV. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 Methodology of this systematic review and inclusion criteria were indicated in advance and recorded in a priori protocol in order to determine the rationale, the objectives, the eligibility and selection criteria, the search strategy and the study selection process of this systematic review. However, due to emergency of the subject and due to the pandemic awareness for COVID-19, this systematic review was not registered with PROSPERO (International Prospective Register of Systematic Reviews). All study design types were considered in this systematic review. Reviews were not included but screened for any information within the scope of this review. No language, publication status or publication year restrictions were imposed. As because of the COVID-19 emergency state, even not proofread publications were included in our study. All non-English studies, including Chinese, Japanese and French were translated via Google translator and were included in this systematic review. Although COVID-19 concerns years 2019 and 2020, no year of publication limit was applied, in order to exploit valuable information concerning the coronavirus relationship with environmental factors, as indicated by the past SARS and MERS lessons. All studies included, concern human coronavirus strains of various types. This systematic review was limited to studies focusing to environmental factors' impact on COVID-19. Searched experts' and researchers' opinions were not handed in this study. The selection criteria developed a priori are described below: • Year of publication (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 The search strategy and analysis process were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement for systematic reviews (Liberati et al. 2009; Page et al. 2018) . Titles and abstracts of the retrieved articles were screened, while full length articles were evaluated for eligibility and were further acquired via SwetsWise Online Content. Search for articles was applied in three electronic databases: Google Scholar, PubMed & Springerlink. Google Scholar was our starting point. No unpublished information obtained. The literature search was performed from 25 to 28 of March 2020. The following terms were used to search all databases, always in combination with "coronavirus" and "COVID-19": "environmental factors", "clima", "temperature", "humidity", "absolute humidity", "relative humidity", "wind speed", "wind power", "precipitation", "rainfall". The search strategy was conducted by IPC and was peer-reviewed by AV as part of the systematic review process. Eligibility assessment procedure was performed in standardized and independent manner, primary by two authors (IPC and AV), to analyze and validate all relevant data to the top under discussion. Disagreements were resolved through discussion among all authors and resulted in a final consensus. After excluding records upon the eligibility criteria set, we screened all titles and abstracts of the retrieved studies, although full text review proves also to be necessary for further consideration. A data extraction sheet was developed in order to summarize the evidence of this systematic review, based on the Cochrane Consumers and Communication Review Group' data extraction All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 template for included studies (Cochrane Consumers and Communication 2016) . This was pilot tested on the first ten randomly selected studies and no refinement was needed. One author (IPC) extracted all proper data from the included studies and another author (AV) checked all the extracted data. No disagreements arose. In order to ascertain duplicate publications, we used the tool "check for duplicates" of Mendeley Desktop software (Version 1.19.4). To ascertain the validity of the included studies, two reviewers (IPC and AV) in a blind manner and independently scored the included papers' quality upon the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist (Von Elm et al. 2014 ). Both reviewers independently scored each included paper's quality and all studies received a score that ranged from 0 to 22 points by each reviewer. Base up on a criterion included in the initial protocol of the study, the scores between the reviewers should not differ from one to another reviewer by more than 2 points. In order to generate a final score, both scores of the reviewers were averaged. In order to handle data and combine the results of all the included studies, we used SPSS (Statistical Package for the Social Sciences) (IBM SPSS Statistics for Macintosh, Version 25.0 n.d.) or R software (R Development Core Team 2013). All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020. . https://doi.org/10.1101/2020.05.10.20069732 doi: medRxiv preprint The search of Google Scholar, Springerlink and PubMed provided a total of 14640, 51 and 28 articles, respectively. From the initially obtained 14719 articles, 8499 were excluded as duplicated ones upon "Check for duplicates" tool of Mendeley Desktop. The remaining 6220 articles were assessed for eligibility and a total of 6007 articles were discarded because based on a detailed evaluation of abstracts, they did not meet the eligibility criteria set and concerned: All 23 studies selected for this systematic review were published in 2020 and in English. 65.2% of the included studies reported China, 26.1% did not mention a certain country of epidemics, 4.3% concerned the epicentre of the disease, namely Iran, Italy, South Korea, etc. and 4.3% concerned Singapore. Upon continent of epidemics, Asia hold the leads with 69,6%, followed by Africa with 4.3%, whereas almost 21.7% did not mention specific continent and 4.3% refers to mixed continents (Asia, Europe, etc.). All included studies assessed the role of various environmental factors on transmission rates of the COVID-19. In 24.1% of the studies, temperature was assessed for its impact on COVID-19, followed by humidity (11.1%), absolute humidity (5.6%), rainfall/precipitation (5.6%), relative humidity (5.6%), travel (5.6%), air travel (3.7%), wind speed/power (3.7%), latitude (3.7%), built All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020. . https://doi.org/10.1101/2020.05.10.20069732 doi: medRxiv preprint environment (1.9%), general lockdown (1.9%), visibility (1.9%), specific humidity (1.9%), airborne dust (1.9%), air pollution (1.9%), chemical pollution (1.9%), air index (1.9%), atmospheric radiation (1.9%), cloud cover (1.9%), precipitation of the driest month (1.9%), mean temperature of the wettest quarter (1.9%), isothermality (day-to-night temperatures difference relative to the summer-to-winter annual difference) (1.9%), annual mean temperature (1.9%), mean diurnal range (1.9%), minimum temperature of the coldest month (1.9%) and precipitation of the coldest quarter (1.9%). In order to examine the association between those environmental factors and COVID-19, most of the studies employed the review method (20.4%), followed by maximum entropy model (13%), the model (11.1%), dynamical model and ERA-5 reanalysis (9.3%), the statistical modeling Loess regression (Generalized-linear or non-linear model) (7.4%), the R proxy method (5.6%), the R reproductive number (3.7%), the One-way ANOVA followed by a post-hoc Tukey's HSD test (3.7%), the distributed lag log-linear model (3.7%), the linear regression model (3.7%), the global meta-population disease transmission model (3.7%), the Mann-Whitney U test (3.7%), the mathematical model (3.7%), the restricted cubic spline function and the generalized linear mixture model (3.7%) and the multivariate analysis (3.7%). Figure 2 displays the environmental factor assessed, combined with the assessing method and the country of epidemics it concerns. Detailed characteristics of the studies included, like author, title and year of publication, country and continent of the study, method of assessing the impact of the environmental factors and the outcome variable are described in Table 1 . (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020. The studies included in this systematic review were scored from 17 to 19.8, upon the criteria predefined. The criteria on which studies were assessed with the minimum score were related to their not clearly addressing the following items: report of the study design and assessing method All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 1 2 in the title and abstract; clearly define the participants, the interventions and the outcomes; clearly state handle of missing data and accuracy of data; generalization of the findings. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 To the best of our knowledge, the present systematic review is the first to summarize the available evidence on the association of COVID-19 with environmental factors. Taking into consideration that the new coronavirus is a new human pathogen, which due to its outbreak in China and its rapid spread worldwide, it is important to understand reliable epidemiological information for its survival in the environment (Chen et al. 2020) . Therefore, it is necessary to find prognostic predictors to distinguish high-risk areas or countries and improve the new (Bu et al. 2020) . Concerning humidity, although the results in this review did not reveal robust associations between humidity and coronavirus survival and are always validated in combination with temperature, they need to be interpreted carefully given the monotonic functional relationship between humidity and temperature. In other words, if temperature was associated to COVID-19 transmission, very likely absolute humidity would play a role. Pooled results of the studies included in this systematic review show that combined All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020. . with high temperature, absolute humidity range of 4-7 g/m 3 (Sajadi, Habibzadeh, Vintzileos, Miralles-wilhelm, et al. 2020) or specific humidity range of 3-6 g/kg (Sajadi, Habibzadeh, Vintzileos, Miralles-wilhelm, et al. 2020) Apart from the he basic strengths of this review regards the study quality assessment, which was based on STROBE, its PRISMA compliance approach and the peer-review process followed. 1 5 Due to limited data available, other meteorological factors such as air pressure, atmospheric particles, ultraviolet, and social factors such as population movement were not included for analysis. Inclusion of such factors will provide more accurate and reliable results. In addition, the relatively short time length of the current outbreak, combined with imperfect daily reporting practices, make our results vulnerable to changes as more data becomes available. We have assumed that travel limitations and other containment interventions have been implemented consistently across provinces and have had similar impacts (thus population mixing and contact rates are assumed to be comparable), and have ignored the fact that different places may have different reporting practices. Further improvements could incorporate data augmentation techniques that may be able to produce historical time series with likely estimates of case counts based on onset of disease rather than reporting dates. This, along with more detailed estimates of the serial interval distribution, could yield more realistic estimates of R. Finally, further experimental work needs to be conducted to better understand the mechanisms of transmission of COVID-19. Mechanistic understanding of transmission could lead to a coherent justification of our findings. In summary, this review provided evidence that high temperature and high humidity reduce the COVID-19 transmission. However, further studies concerning other environmental (namely meteorological) factors' role should be conducted in order to further prove this correlation. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020. . https://doi.org/10.1101/2020.05.10.20069732 doi: medRxiv preprint Figure 2 Temperature associated with the assessing methods the country of epidemics All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 15, 2020 . . https://doi.org/10.1101 Figure 2 Environmental factors associated with the assessing methods the country of epidemics All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 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No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.