Infectious and Non-infectious Diseases: The Lines Begin to Blur

written by Elise Miller, MEd

Deaths from noncommunicable diseases (NCDs) were estimated at 68% in 2012 globally, up from 60% in 2000, while deaths from infectious diseases are decreasing. This is according to the second edition of the World Health Organization’s report, “Preventing disease through healthy environments: a global assessment of the burden of disease from environmental risks“, published last month. The researchers found that environmental risk factors, including chemical exposures, pollutants in air, water and soil, climate change, and ultraviolet radiation, were primary contributors to these deaths.

What this tells us is the huge investment in preventing infectious diseases from philanthropic organizations, like the Bill and Melinda Gates Foundation, is making a real difference, particularly in low- and middle-income countries. This also suggests that we are not doing nearly enough to address far more intractable and pervasive concerns that lead to NCDs, such as ensuring people have clean drinking water. It’s easier to distribute vaccines than, say, stop the use of pesticides, take the lead out of pipes, or prevent coal-burning power plants from being built.

Enumerating the number of deaths also doesn’t account for the millions of people who suffer from chronic conditions that don’t necessarily lead to death, such as learning and developmental disabilities or reproductive health problems. Those of us working in the field of environmental health know that environmental risk factors can play a role in these as well, but the toll on individuals, communities, and societies is usually not as immediately obvious as from infectious diseases. This is because health outcomes from chronic and low-dose toxic exposures can take years or even decades to manifest.

In addition, what’s becoming increasingly clear is that deaths from infectious diseases and NCDs can’t always be divided into two neat categories. Instead, leading researchers are finding multiple contributors to disease often interact in a complex array of causal relationships. An infectious agent may be present, but other noncommunicable factors influence whether and what kind of disease may result. For example, endocrine disrupting chemicals can undermine the healthy functioning of the immune system, making a person more likely to contract an infectious disease.

Overall this means that even more deaths may be the result of exposure to environmental risk factors than is being currently calculated. If we increased funding for studies that could help us determine how multiple, interacting factors—including the chemical environment, viral agents, and socioeconomic status—result in disease and disability, we could then develop an algorithm to show the proportion of deaths that had both infectious and noninfectious contributors as well. And even more important, we could develop and invest in more effective upstream interventions that could decrease both.

To truly improve global health in the 21st century, the fact is we have to look beyond the rigidly defined categories and areas of expertise that have previously served to advance Western science. Instead, we now need to blur the lines some and explore the complexity of relationships between what we deemed earlier to be distinct and immutable. Systems approaches not only reflect the truth of our reality, but make it more likely that creative solutions will emerge that simultaneously address multiple, interacting factors to reduce disease incidence and boost resiliency and well-being. By doing so, perhaps 10 years from now when the third edition of WHO’s report is published, we could see the numbers for not only infectious diseases, but NCDs on the decline.


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