key: cord-0727044-f4k7t9sp
authors: Crema, Edilson
title: The SARS-COV-2 outbreak around the Amazon rainforest: the relevance of the airborne transmission.
date: 2020-12-08
journal: Sci Total Environ
DOI: 10.1016/j.scitotenv.2020.144312
sha: d86a136ac9d493b3d9d3d840546f7357e2ef256f
doc_id: 727044
cord_uid: f4k7t9sp

At the beginning of the SARS-COV-2 outbreak in Brazil, there was a striking difference between the contamination rate in the Amazonian States and the South and the Southeast States. The regions near the Amazon rainforest presented much higher and faster contaminations. This paper attempts to explain this phenomenon through a global analysis of the COVID-19 epidemic in Brazil. It also investigates the relationship between climate conditions and airborne transmission with the evolution of contagion in the Amazonian states. The method of investigation of the spread of SARS-COV-2 in these different macro-environments was based on the analysis of three extensive daily official databases on the number of deaths, the percentage of adherence of the populations to the restriction policies, and the local climatic conditions. Besides, the social conditions in those States were also taken into account. Then, it was compared the epidemiologic results for States with very different climatic characteristics and that had adopted, almost simultaneously, similar social isolation measures. However, all these analyses were not able to explain the remarkable difference in the evolution of the pandemic among Brazilian regions. So, it was necessary to invoke airborne transmission, facilitated by the very high air humidity, as a decisive factor to explain the faster evolution of contagion in the rainforest region. Air humidity seems to be the most important climatic factor in viral spreading, while usual ambient temperatures do not have a strong influence. Another very important result of this analysis was the observation that the onset of collective immunity may have been achieved with a contamination rate of about 15% of the Amazonian population.

important climatic factor in viral spreading, while usual ambient temperatures do not have a strong influence. Another very important result of this analysis was the observation that the onset of collective immunity may have been achieved with a contamination rate of about 15% of the Amazonian population.

The ray of light that runs through a dark room reveals the existence of numerous small grains of dust that can float in the air for a long time. Since antiquity, this Currently, this phenomenon has gained tragic relevance due to the uncontrolled dispersion of the Covid-19 throughout the planet, since airborne transmission is one of similar situation occurred with the Influenza virus. While some important books and works drew attention to the relevance of the transmission by aerosols, [3] [4] [5] [6] other authors argued that short-distance transmission by drops would be the main means of infection, 7, 8 and this latter position prevailed for a long time among health authorities who practically ignored airborne transmission. 9,10 At the end of March 2020, the World Health Organization (WHO) released a bulletin stating that there was insufficient scientific evidence that SARS-COV-2 was significantly airborne transmitted. A few months ago, at the beginning of the current pandemic, several governments and the most important health authorities on the planet recommended that only hand washing and a distance of two meters between people would be safe protection procedures and that the use of masks was unnecessary throughout the population. However, with the rapid spread of the coronavirus in countries and in the world, the deadly reality has imposed itself and forced the health authorities to reverse this directive, saving thousands of lives by requiring the use of masks in several countries. From a scientific point of view, this late change in positioning was the authorities' recognition that air transmission of SARS-COV-2 is an unquestionable fact. Nevertheless, it remains to be understood how this process takes place.

Every global health crisis is a medical, epidemiological, scientific, political, social, and economic event. 11 Only a multidisciplinary approach can fully understand this planetary event. This article is a contribution to this multidisciplinary scientific effort, discussing one of the most important scientific facets of viral transmission. It will be analyzed the SARS-COV-2 outbreak around the Amazon rainforest that may help to understand the relevance of the long-range viral airborne transmission. Amazonian

States have a much higher contamination rate than the Southern and Southeastern States. The study of the Amazon region is particularly interesting because it has very high air humidity that can facilitate the survival of the virus in the external environment.

The airborne transmission of the coronavirus is now experimentally well analyzed the air at the Nebraska Hospital Center and also found the SARS-COV-2 in most environments occupied by patients with mild and moderate infections. 13 In these two studies it was not possible to confirm if these viruses were active. However, this doubt was finally resolved by a study published in the New England Journal of Medicine, where the presence of active SARS-COV-2 in droplets was observed more than three hours after they were artificially produced in the laboratory (65% of relative humidity and temperatures between 21-23ºC). 14 Now, it is certain that under normal day-to-day conditions SARS-COV-2 remains active for hours in the droplets suspended in the air. Extensive study published in The Lancet journal, analyzing empirical data from 16 countries on six continents, concluded that the probability of infection by SARS-CoV-2 decreases by 10,6% when using a protection for the eyes. 15 That is, the risk of contagion through the eyes is very high and continues to be minimized by health authorities, including the WHO, as had happened in the case of masks. This may be a new mistake in combating the pandemic.

On the other hand, further experiments visualized the production of saliva droplets during a person's normal speech, breathing, sneeze and cough. [16] [17] [18] Thousands of drops were exhaled and their dispersion in the air was video recorded. They used a laser beam technique of high resolution that was able to identify even submicron droplets. In the video from Kyoto University, 19 one can watch the movement of these drops, revealing that while the larger ones fall rapidly and settle on the ground and furniture, there are hundreds of micro droplets that remain suspended in the air several hours after being exhaled. And, most seriously, these small drops disperse rapidly and, a few minutes after their production, occupy the entire environment, covering distances greater than eight meters. was 13% and 15%, respectively. In other cities near the rainforest this percentage attained 20% to 25%. 24 Therefore, the contamination rate that could have produced the interruption of the spread of the epidemic observed in Fig. 1 was only of the order of 15%. If confirmed by further studies, this result could be very useful in combating the pandemic.

The striking difference observed between the North and South regions could not be explained by the issue of social isolation measures, since both adopted, almost simultaneously, similar isolation measures. However, a determining factor in viral dissemination is the degree of adherence of the population to the measures adopted. To investigate this factor, it was analyzed daily geo-localized mobile phone data that evaluate social mobility. 25 Figure 2 shows the result of the average social isolation, per week, calculated in the period investigated in this paper. As can be seen in this figure 

Other possible explanation for a rapid evolution of the epidemic would be a high population concentration. Figure 3 shows the number of inhabitants and population density in the States under investigation. 26 As it can be seen, the States in the Amazon region, Amazonas and Pará, have a smaller population and much lower population density (inhabitants/km 2 ) than the Southern and Southeastern States. Therefore, from this point of view, one would expect contamination to be faster in states with higher population density, contrary to what happened. Fig. 1 . So, the remarkable disparity in the evolution of the contamination in these regions needs to be deeply investigated. Source of primary data: Instituto Brasileiro de Geografia e Estatística (IBGE).

A factor that can play an important role in the spread of SARS-COV-2 is the climate. During the months investigated in this work, in the regions surrounding the forest, the average temperatures were always above 30ºC and the average relative humidity, above 80%. In southern States, average temperatures and average relative humidity were not higher than 22ºC and 50%, respectively. Therefore, there is no direct relationship between high ambient temperature and decreased transmissibility. On the other hand, some studies showed that, in general, in environments with relative humidity above 60%, approximately, the drops absorb more than evaporate water into the air. 27, 28 So, one can suppose that the airborne transmission of the SARS-COV-2, facilitated by the high humidity of the air, could be a primary factor in the development J o u r n a l P r e -p r o o f of the epidemic in Brazil. This hypothesis is confirmed by other studies conducted in some cities in Brazil at the beginning of the pandemic, although these studies use the number of cases as an analysis variable. 29, 30 To better understand this relationship, it is interesting to know the amount of water vapor that actually exists in the atmosphere, that is, its absolute humidity. One kilo of air with relative humidity 70%, at 30ºC, contains approximately 19g of water in the form of vapor, while at a relative humidity of 40%, at 22ºC, the amount of water is only 6g. A similar situation has occurred in abattoirs in France, Germany, and the USA that have become huge poles of contamination. The dominant explanation for this phenomenon has been the airborne transmission facilitated by the low temperature of these environments. However, the pandemic evolution in Brazil, Middle East, Europe, China, and USA has demonstrated that habitual temperatures seem to have little influence on the survival of the virus in the external environment. Therefore, as in the Amazonian case, one can suppose that also in the abattoirs the most important factor was the very high humidity of the air needed in these environments. These examples confirm old and classical work that showed the existence of a very complex relationship between coronavirus survival and air temperature and humidity. 32

The very high SARS-COV-2 transmission rates in Amazonian States in Brazil and many abattoirs around the world provide empirical corroboration of the relevance of the airborne way of contagion. These two environments have high air humidity that allows viruses to survive much longer in droplets in suspension or deposited on surfaces. Therefore, air humidity seems to be the major climatic factor in the development of the COVID-19 epidemic. On the other hand, apparently, there is no direct relationship between high ambient temperature and decreased transmissibility.

Besides, the onset of collective immunity in Amazonian States may have been achieved with a contamination rate of around 15% of the population, much lower than predict J o u r n a l P r e -p r o o f Journal Pre-proof

Nature des choses (Éditions Gallimard, Essais Folio

Influenza virus" in Douglas and Bennett's principles and practice of infectious diseases

Airborne transmission of SARS-CoV-2: The world should face the reality

It is Time to Address Airborne Transmission of COVID-19

WHO Writing Group: Nonpharmaceutical interventions for pandemic influenza, international measures

Transmission of influenza A in human beings

Public Health Agency of Canada Canadian Pandemic Influenza Plan (Appendix F)

Department of Health and Human Services Pandemic Influenza Plan

Commercial exchanges instead of air pollution as possible origin of COVID-19 initial diffusion phase in Italy: More efforts are necessary to address interdisciplinary research

Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals

Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1

Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19

The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission

Toward Understanding the Risk of Secondary Airborne Infection: Emission of Respirable Pathogens

Environmental Transmission of SARS at Amoy Gardens

Extensive Viable Middle East Respiratory Syndrome (MERS)

Coronavirus Contamination in Air and Surrounding Environment in MERS Isolation Wards

COVID-19 Outbreak Associated with Air Conditioning in Restaurant

Identifying airborne transmission as the dominant route for the spread of COVID-19

Mechanistic insights into the effect of humidity on airborne influenza virus survival, transmission and incidence

Absolute humidity modulates influenza survival, transmission, and seasonality

Evidence that high temperatures and intermediate relative humidity might favor the spread of COVID-19 in tropical climate: A case study for the most affected Brazilian cities

Association between climate variables and global transmission of SARS-CoV-2

Instituto Nacional de Meteorologia (INMET)

Survival Characteristics of Airborne Human Coronavirus 229E

conventional statistical studies. If corroborated by other research, this result will have an important impact on the management of the pandemic.

Author contribution This paper was conceived and written by only one author.J o u r n a l P r e -p r o o f