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      COVID-19 in Latin America: Novel transmission dynamics for a global pandemic?

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          The COVID-19 virus expanded from China into Western Asia, Europe, and North America, impacting many of the world’s wealthiest countries. Brazil reported Latin America’s first case in late February 2020, and in less than a month, over 7,000 COVID-19 cases have been confirmed among nearly every country and territory in Latin America and the Caribbean (LAC). The LAC outbreak appears to be about two weeks behind the United States and Canada and about three to four weeks behind Western Europe. Thus, the global COVID-19 pandemic is entering a new phase, not only expanding beyond primarily temperate Northern Hemisphere countries into the tropics but also spreading to a geopolitical region marked by significantly worse poverty, water access and sanitation, and distrust in public governance (Fig 1). We believe that these aspects of the Latin American context are likely to substantially affect the transmission dynamics and scope of the COVID-19 outbreak in LAC, with potential implications for the trajectory of the global pandemic. 10.1371/journal.pntd.0008265.g001 Fig 1 Socioeconomic differences between “First 15” COVID-19 countries and LAC. Significant differences are found in the HDI [23], WPI [24], and CPI [25] between the first 15 (“First 15”) countries where COVID-19 was recorded to have expanded rapidly out of China (blue) and the 15 most populous countries in LAC (red). HDI: (Welch-corrected t test; AverageFirst 15 = 0.907; AverageLAC = 0.721; P < 0.0001); WASH: (Welch-corrected t-test; AverageFirst 15 = 95.11; AverageLAC = 49.17; P < 0.0001); CPI: (Welch-corrected t-test, AverageFirst 15 = 70.9; AverageLAC = 33.87; P < 0.0001). We classified “First 15” countries as the 15 non-Chinese countries with the highest reported number of COVID-19 cases in the March 8, 2020 COVID-19 Situation Report [26]. CPI, Corruption Perceptions Index; HDI, Human Development Index; LAC, Latin America and the Caribbean; WASH, Water, Sanitation, and Hygiene; WPI, Water Poverty Index. COVID-19, temperature and humidity, and transmission One of the most important questions in COVID-19 global epidemiology is whether warmer temperature and higher humidity impedes transmission. The initial countries to experience the largest increase in day over day new COVID-19 cases experienced cold and dry conditions typical for wintertime in temperate Northern Hemisphere. Among Chinese cities, the COVID-19 basic reproductive number (R) appears to be inversely related with temperature and relative humidity, albeit with substantial variation [1]. One early travel-based model of COVID-19 global spread predicted that several southeastern Asian countries should have been the first non-Chinese countries to experience substantial COVID-19 outbreaks [2]. Instead, substantial outbreaks outside China occurred first in Western Asia and Europe. Additional support for the hypothesis that higher temperature and humidity dampens COVID-19 transmission comes from laboratory experiments on the severe acute respiratory syndrome (SARS) virus and other coronaviruses, which found that increasing temperature and humidity decreases the virulence of dried virus on smooth surfaces [3]. Some commentators have suggested that COVID-19 transmission may decline as the Northern Hemisphere transitions to summer, as happens with seasonal influenza. However, as demonstrated by 2009 H1N1 influenza, novel pandemic respiratory virus transmission dynamics are often decoupled from the climatic conditions that drive the seasonality of influenza [4]. While seasonal influenza does vary with temperature and humidity in LAC, the region’s environmental heterogeneity causes peaks in influenza transmission to be asynchronous across the region [5]. Thus, although environmental conditions in March 2020 appear to be less favorable for COVID-19 transmission across most of LAC, by July 2020 many South American cities have climatic conditions that would appear more favorable for rapid COVID-19 transmission [1], coinciding with a strong peak of seasonal influenza transmission in subtropical South America between May and October [6]. Therefore, while the environmental models suggest that LAC’s higher temperature and humidity may slow the initial COVID-19 transmission, this effect may be ephemeral for much of the region. Any tropical climate effect may also be limited by the ubiquity of indoor air conditioning, which creates indoor environments with temperature and humidity ranges favorable to coronavirus persistence [3]. Most importantly, climate-based transmission models assume COVID-19 spreads primarily via indirect surface contact transmission. We believe that other transmission models (especially fecal–oral) may be as or more important for COVID-19 transmission in LAC, making predictions from climate models premature. The potential for increased fecal–oral COVID-19 transmission in LAC Although a respiratory disease, COVID-19 is likely transmissible via fecal–oral contamination. While only a portion of Wuhan patients experienced gastrointestinal symptoms, these generally presented prior to respiratory symptoms [7]. Fecal swabs test positive using reverse transcription PCR (RT-PCR) for COVID-19 virus in slightly more than half of sampled patients [8], and stool samples remained positive for an average of 11 days after respiratory swabs turned negative [8]. During the Middle East respiratory syndrome (MERS) and SARS (and now COVID-19) coronavirus epidemics, patients often experienced gastrointestinal symptoms, and these viruses were detected in stool samples and shown to infect and replicate in intestinal tissues [9]. A large SARS outbreak in a Hong Kong apartment complex is believed to be due to virus particles that were aerosolized from improperly installed wastewater pipes [10]. Finally, molecular modeling suggests that the COVID-19 (like MERS and SARS) uses the angiotensin-converting enzyme II (ACE2), which is highly expressed in both lung and some intestinal epithelial tissues [11] as its host receptor. Collectively, this suggests that fecal–oral transmission will probably be important for COVID-19 spread [9]. Thus, LAC will be the first region where water scarcity and poor sanitation may substantially impact COVID-19 spread. The World Bank estimates that 36 million people in LAC lack access to improved drinking water, and 110 million lack access to improved sanitation [12]. In LAC urban slums, the lack of in-house water delivery results in reduced water usage, limited handwashing, and poor family hygiene, leading to widespread fecal contamination [13]. In LAC households without clean water delivery, drinking water is often boiled and stored; yet this water often becomes fecally contaminated [13]. Importantly, coronaviruses can remain infectious for weeks in room temperature water [14]. Like poor clean water access, inadequate sewage disposal causes chronic fecal contamination and disease in LAC, even when improved water is available [15]. Many LAC countries score poorly on the WASH index, which is a measure of access to abundant clean water and improved sanitation. If increased transmission due to fecal contamination is combined with climatically reduced contact transmission, the epidemiological dynamics of COVID-19 in LAC may be fundamentally distinct from the dynamics currently observed in the Northern Hemisphere. We can look to the epidemiological characteristics of norovirus and cholera in LAC for insights. In LAC slums with poor water access and sanitation, over 80% of children are infected with at least one strain of norovirus in their first year of life [16]; adults are only infected when novel genotypes enter the community. Cholera is a disease of poverty exacerbated by poor access to clean water. During the 1991 cholera epidemic in Peru, cholera spread nearby instantaneously from a single town to nearly communities along the Peruvian coast with attack rates over 2% in just the first month of the epidemic [17]. Because cholera is often transmitted via contaminated stored water and food, up to half of all family members show signs of infection within two days of the presentation of an index case [18]. If COVID-19 spreads in a similar fashion, we can expect increased intrafamily and intraneighborhood infection rates. Like norovirus, this may result in rapid herd immunity within infected communities [16]; however, with a large peak of simultaneous infections, local health centers will almost certainly be overwhelmed. Extreme rates of local infection can cause complex metapopulation dynamics that could favor rapid local eradication while at the same time facilitating long-term regional viral persistence [19]. In the face of this, LAC will need to implement widespread population surveillance of both active cases (using RT-PCR) and prior exposure and potential immunity via serology. COVID-19, weak infrastructure, and poverty COVID-19 expanded from China into some of the world’s richest countries (Fig 1), perhaps masking socio-economic factors in the outbreak’s spread. During recent epidemics, LAC’s poor were more likely to become infected with Zika and more likely bear children with microcephaly [20], suggesting that the burden of COVID-19 may be disproportionately borne by LAC’s poorest and most marginalized. Health infrastructure is weak and inadequate in LAC, where epidemics routinely overwhelm a public health system that suffers from chronic understaffing and a lack of modern medical equipment and diagnostic and therapeutic consumables, including personal protective equipment. If the COVID-19 epidemic in LAC is severe, it is probable that the region will come out of the epidemic even more inequitable than it is now. Thus, the imperative to “flatten the curve” is even greater for LAC than Western Europe and the United States. Not surprisingly, several LAC countries rapidly implemented strict social restrictions (“lockdowns”) to curb transmission, including complete border closures, restricted daytime movements, night-time curfews, and the cessation of intraprovincial travel. Evidence from China suggests that such extreme restrictions should reduce transmission and blunt COVID epidemics. But will LAC citizens comply? Public distrust of government is significantly higher in LAC than in the first countries to experience COVID-19 spread out of China (Fig 1), and this distrust has been shown to erode compliance with public health societal restrictions [21]. Collectively, the interactions between climate, WASH conditions, and other socioeconomic factors suggest that the impacts of COVID-19 in LAC will be more extreme than even that experienced by Western Europe and the United States. Experimental studies and modeling efforts should focus on alternative COVID-19 transmission dynamics, and LAC’s leaders must continue to take immediate and decisive actions to slow the spread of COVID-19. Extreme regulation of social distancing may be required. Fortunately, several commercial ELISA tests predict neutralizing antibody levels for COVID-19 [22]. Widespread serological testing will allow citizens with developed immunity to return back into society and the economy.

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          Most cited references 9

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          Seasonality of influenza in Brazil: a traveling wave from the Amazon to the subtropics.

          Influenza circulation and mortality impact in tropical areas have not been well characterized. The authors studied the seasonality of influenza throughout Brazil, a geographically diverse country, by modeling influenza-related mortality and laboratory surveillance data. Monthly time series of pneumonia and influenza mortality were obtained from 1979 to 2001 for each of the 27 Brazilian states. Detrended time series were analyzed by Fourier decomposition to describe the amplitude and timing of annual and semiannual epidemic cycles, and the resulting seasonal parameters were compared across latitudes, ranging from the equator (+5 degrees N) to the subtropics (-35 degrees S). Seasonality in mortality was most pronounced in southern states (winter epidemics, June-July), gradually attenuated toward central states (15 degrees S) (p < 0.001), and remained low near the equator. A seasonal southward traveling wave of influenza was identified across Brazil, originating from equatorial and low-population regions in March-April and moving toward temperate and highly populous regions over a 3-month period. Laboratory surveillance data from recent years provided independent confirmation that mortality peaks coincided with influenza virus activity. The direction of the traveling wave suggests that environmental forces (temperature, humidity) play a more important role than population factors (density, travel) in driving the timing of influenza epidemics across Brazil.
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            Effect of water and sanitation on childhood health in a poor Peruvian peri-urban community.

            Inadequate water and sanitation adversely affect the health of children in developing countries. We aimed to assess the effects of water and sanitation on childhood health in a birth cohort of Peruvian children. We followed up children once a day for diarrhoea and once a month for anthropometry, and obtained data for household water and sanitation at baseline. At 24 months of age, children with the worst conditions for water source, water storage, and sanitation were 1.0 cm (95% CI 0.1-0.8) shorter and had 54% (-1 to 240) more diarrhoeal episodes than did those with the best conditions. Children from households with small storage containers had 28% (1-63) more diarrhoeal episodes than did children from households with large containers. Lack of adequate sewage disposal explained a height deficit of 0.9 cm (0.2-1.7) at 24 months of age. Better water source alone did not accomplish full health benefits. In 24-month-old children from households with a water connection, those in households without adequate sewage disposal and with small storage containers were 1.8 cm (0.1-3.6) shorter than children in households with sewage and with large storage containers. Our findings show that nutritional status is a useful endpoint for water and sanitation interventions and underscores the need to improve sanitation in developing countries. Improved and more reliable water sources should discourage water storage at risk of becoming contaminated, decrease diarrhoeal incidence, and improve linear growth in children.
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              Clinical outcomes in household contacts of patients with cholera in Bangladesh.

              Multiple Vibrio cholerae infections in the same household are common. The objective of this study was to examine the incidence of V. cholerae infection and associated clinical symptoms in household contacts of patients with cholera and to identify risk factors for development of severe dehydration in this cohort. Household contacts of hospitalized patients with cholera were observed with frequent clinical assessments and collection of serum and rectal swab samples for culture for a period of 21 days after presentation of the index case. One-half (460 of 944) of all contacts reported diarrhea during the study period, and symptoms most frequently began 2 days after presentation of the index case. Antibiotics were used by 199 (43%) of 460 contacts with diarrhea. Results of rectal swab cultures for V. cholerae were positive for 202 (21%) of 944 contacts, and 148 (73%) infected contacts experienced diarrhea. Significant dehydration developed in 26 contacts; predictors of dehydration included vomiting, each additional day of diarrhea, and blood group O status. In urban Bangladesh, the burden of diarrheal illness among household contacts of patients with cholera is higher than was previously estimated, and prophylactic intervention is feasible, because the majority of symptomatic cases of V. cholerae infection in contacts begin soon after presentation of the index case. Re-evaluation of targeted chemoprophylaxis for household contacts of patients with cholera may be warranted.

                Author and article information

                Role: Editor
                PLoS Negl Trop Dis
                PLoS Negl Trop Dis
                PLoS Neglected Tropical Diseases
                Public Library of Science (San Francisco, CA USA )
                7 May 2020
                May 2020
                : 14
                : 5
                [1 ] University of Oklahoma, Norman, Oklahoma, United States of America
                [2 ] University of Alaska Fairbanks, Fairbanks, Alaska, United States of America
                [3 ] INDICASAT-AIP, City of Knowledge, Republic of Panama
                [4 ] Smithsonian Tropical Research Institute, Balboa, Republic of Panama
                [5 ] John Hopkins University, Baltimore, Maryland, United States of America
                London School of Hygiene & Tropical Medicine, UNITED KINGDOM
                Author notes

                The authors have declared that no competing interests exist.

                © 2020 Miller et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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                The author(s) received no specific funding for this work.
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