Environmental health and infectious diseases: challenges and perspectives in Latin America

Environmental health (EH) is defined as an area of public health dedicated to assessing the risks and harms to health resulting from environmental degradation and pollution and proposing and evaluating programs for their reduction. According to the World Health Organization (WHO), EH is related to healthier environments that could prevent almost one-quarter of the global burden of disease. Also, clean air, a stable climate, adequate water sanitation and hygiene, safe use of chemicals, protection from radiation, healthy and safe workplaces, sound agricultural practices, health-supportive cities, built environments, and a preserved nature are all prerequisites for good health. ¹

WHO estimated that some 24% of disability-adjusted years of healthy life was lost and 23% of premature deaths worldwide were caused by exposure to avoidable environmental risks, ¹ with one-third of the deaths being children under 5 years old. Also, environmental factors might play a role in more than 80% of major diseases and injuries around the world and are among the biggest killers. Diseases with the largest environmental contribution in children under the age of 5 years include lower respiratory infections (32%), neonatal conditions (15%), and infectious diseases as diarrheal diseases (22%) and parasitic and vector-borne diseases (12%). ² In the Americas, the estimated disease burden from preventable environmental causes (17%) significantly undermined health services, financial stability, economic growth, and governance in the broadest sense. ³

According to projections, the world’s population will rise to 9.1 billion by the mid-21st century. ⁴ If this trend continues, the people of Latin America and the Caribbean will reach an estimated 751 million by 2050, equivalent to 8.3% of the global population. ⁵

Also, the Americas are already the world’s most urbanized region. In 2010, 82.1% of North America’s population and 79.4% of that of Latin America and the Caribbean lived in urban areas. Recent data show that although urban growth in Latin America and the Caribbean began to slow between 2005 and 2010, it is predicted that by 2025, 9 of the world’s 30 largest cities will be in the Americas: São Paulo, Mexico City, New York, Buenos Aires, Los Angeles, Rio de Janeiro, Bogotá, Lima, and Chicago. ⁶

We have a substantial debt stock in environmental terms in Latin America and the Caribbean, especially regarding EH. While some of the region’s countries have improved their national health services, most have found it impossible to introduce robust intersectoral health reforms due to their persistent sector-specific approach to public policies, concepts, and action plans. Although there have been notable improvements in the doctrines, methods, and metrics related to EH and the social determinants of health, the health services in much of the region remain predominantly assistentialist, wedded to narrowly focused conventional prevention and promotion programs, despite the growing evidence that environmental and social factors are primarily responsible for a significant burden of death and disease. ⁷

The growth of cities and urbanization create advantageous conditions for access to socioenvironmental benefits with positive health impacts. However, urban congestion and overcrowding facilitate the emergence and spread of infectious diseases. Emerging and re-emerging pathogens are thought to be the sources of the ever-newer threats of infectious diseases. Climate change, essentially due to global warming, the plundering of the earth’s ecosystem, rising urbanization, deforestation, and encroaching animal habitats shifting land-use patterns, will raise the likelihood of disease outbreaks in the future decades. There is growing evidence that climate change is increasing the incidence and distribution of certain infectious diseases, particularly those transmitted by vectors such as mosquitoes and ticks.^8,9

The main concerns are the unhealthy urban areas typical of the second half of the 20th century. The megacity slums, known variously as favelas, tugurios, villas miseria, comunas or pueblos jóvenes, depending on the country. Migrants from the countryside live in these ramshackle areas, where urban poverty takes hold, accompanied by social disadvantages and inequities. A third of city inhabitants – 1 billion people – reside in these unhealthy urban settings, with deleterious consequences for health, especially in areas where poverty is rife. Between 2005 and 2008, the WHO Commission on Social Determinants of Health (Subcommittee on the Knowledge Network on Urban Settings) devoted significant attention to this issue since, in addition to their dense pockets of poverty, cities reflect the great inequality found in societies. ¹⁰

Urbanization is an irreversible process that, for several centuries, has been making cities responsible for the health of individuals and their communities. Regarding health, cities create opportunities, challenges, benefits, and harm. The benefits include access to essential urban services (drinking water, sanitation, energy, housing), basic social services (health, social protection, safety), and participation in community social networks. The risks of urban development include unhealthy conditions in settlements created with no planning, environmental pollution (mainly air pollution), overcrowding in makeshift dwellings, insecurity, and crime, loss of protective networks due to gang violence, traffic accidents, and a lot of breeding sites for Aedes spp mosquitoes vectors of some infectious diseases like dengue, zika, chikungunya, and so on. It has been known for many centuries that cities’ structural and functional characteristics are essential determinants of health. However, rapid urban population growth has resulted in an uneven distribution of benefits. Inequality and inequity have become the focus of analyses of what is happening in cities.^11,12

In Colombia, the city of Medellín has a population of 2,533,424 inhabitants, distributed in 249 neighborhoods in the urban area and 5 villages. As the capital of the Department of Antioquia and a reference center for health, commercial, and tourism services, the characteristics of the district that generate the need for the Secretary of Health to expand its coverage capacity to guarantee the actions that by law are aimed at preventing, controlling, or reducing health risk factors, especially those related to the supply of services in establishments, vector-borne diseases, zoonotic diseases, water for human consumption and recreational use, and the different eventual problematic situations related to waste, animal ownership, humidity, among others.

The 2021–2023 Development Plan for Medellín includes the EH program, whose description includes favoring and promoting the quality of life and health of the population, present and future generations, and materializing the right to a healthy environment through the positive transformation of social, health, and environmental determinants. The plan includes actions for the promotion, prevention, inspection, surveillance, and control of EH, the dynamization of active participation at the sectoral, intersectoral, interinstitutional, and community levels to seek comprehensive solutions to EH problems, the universalization of public services, surveillance, and control of environmental risk factors, the comprehensive management of watersheds and micro-watersheds in the territory, and the implementation of territorial actions and policies for health adaptation to climate change and variability.

The city has an EH program composed of four components or subprograms: vector-borne diseases, zoonoses, sanitary complaints, inspection, surveillance, and control. These subprograms work in a coordinated manner in pursuit of the common good of EH to benefit the city’s inhabitants. During the operation of the EH program, lessons have been learned to face the challenges of a Latin American city of more than 2 million inhabitants. An initial and very important challenge is the approach to the peripheral areas of misery that have an unplanned growth, with difficulties in access to water and basic sanitation, for which the field teams have acquired great experience in working with communities, but it is still necessary to expand this work much more. A great achievement is related to the vector control program, mainly in the control of Aedes aegypti, a program in which we have been able to consolidate entomovirological surveillance that allows us to focus control actions and avoid the infectious diseases spread by these mosquito vectors.

However, as challenges for the EH governance, this must be redesigned involving a transectoral approach, moving toward the One Health approach. The concept of ‘One Health’, ‘One Medicine’, and ‘One World’ has been reshaped, revived, and refined into their contemporary understanding, which presents an idea where infectious disease can be seen as an outcome derived from multifactorial correlates: animals, plants, ecosystems. and the pathogens that thrive in it. This approach links the disease pathogenesis, environment, pathogens, vectors, and their hosts owing to the existing interdependent, integrated, and symbiotic ecodynamics influencing disease prevalence and can lead to the formulation of health management strategies that are full-proof and broad spectrum.^8,13

Future proposals might include the establishment of a local EH program, updating the situational diagnosis at the regional level to work in conjunction with the nearby municipalities that are adjacent to the city and that have turned the territory into a metropolitan area, strengthening teaching and graduate programs in EH as well as increase support for research in the area and development of an integrated EH surveillance system. Also, it is essential for the city to combine their social, economic, and environmental agendas in a more forward-looking, coherent, and sustainable manner. All of these consider the climate change the world and the country are facing.