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Why Infectious Diseases Still Matter

Sara Gorman explores the interconnectedness of infectious and chronic diseases. 

The headlines are everywhere. “Non-communicable diseases outsmart infectious diseases.“Non-communicable diseases leading cause of deaths worldwide.”Non-communicable diseases take center stage.” Non-communicable diseases are certainly on the rise worldwide and represent a growing concern for global health systems. But are chronic diseases truly taking the place of infectious diseases? In a world of global health systems that tend to focus on one disease or one category of disease at a time, should we be shifting our focus from HIV, tuberculosis, and malaria to asthma, heart disease, and diabetes?

In a thought-provoking article, Alanna Shaikh, a global health professional and writer, convincingly argues “not so fast.” The old view of the epidemiological transition, whereby non-communicable diseases “replace” infectious diseases as the primary threats to health, is probably too simple. Instead, communicable and non-communicable diseases are combining in new ways to present new threats. Shaikh takes the intersection of diabetes and tuberculosis as one prominent example. People with diabetes have a risk for tuberculosis infection 2-3 times greater that among people without diabetes. Even worse, people with diabetes have a higher risk of dying during TB treatment or confronting treatment failure, largely due to the fact that people with diabetes have difficulty tolerating TB drugs. Of course, diseases such as TB and malaria are largely irrelevant in developed countries, but in developing countries, the rise of chronic disease could mean devastating setbacks in the control of infectious diseases.

The diabetes and tuberculosis duo is not the only example of the nasty confluence of communicable and non-communicable diseases. Non-communicable and communicable diseases often share the same risk factors. In fact, the same underlying social conditions, including poverty and unsanitary conditions, may cause both communicable and non-communicable diseases, and there are often significant overlaps in terms of causation and co-morbidity. Some infections cause non-communicable diseases, such as human papilloma virus and cervical cancer.  Treatment of communicable diseases may increase NCD risk, and NCDs and their risk factors may contribute to risk of developing certain infectious diseases.

In some cases, it is clear that communicable and non-communicable diseases function together to create larger health problems, such as maternal and child morbidity and mortality. We have long been aware that infections in pregnancy, such as malaria and HIV, represent major threats to maternal health and also contribute to prematurity and low birthweight. But it is also clear that adverse events in early life significantly increase risk of NCDs later in life. There is even a suggestion that metabolic disease in adult life may be prevented by malaria control in pregnancy. In a case such as maternal and child health programming, it is clear that joint interventions to control both infectious and non-communicable diseases are desperately needed and widespread recognition of the complex interactions between these two categories of diseases is vital.

Given current focus on the rise of non-communicable diseases, there is always a risk that excessively vertical health programs will be implemented. To avoid this, the constant interplay between infectious and non-communicable diseases needs to be recognized and acknowledged and greater integration and resource-sharing in health systems must be pursued. At the primary care level, maternal and child health programs could include interventions to improve nutrition and reduce tobacco use in pregnant and nursing women. Training a wide array of primary health providers to identify and manage hypertension and diabetes in pregnancy would also be essential in reducing risks of both NCDs and infectious diseases in both mothers and children. Reproductive and sexual health programs should include prevention of both sexually transmitted infections and certain kinds of cancer, including breast cancer and cervical cancer. Immunization programs should be expanded to include broad access to HPV vaccines to prevent cervical cancer and Hepatitis B vaccines to prevent liver cancer.

While it is true that devastating non-communicable diseases are on the rise and deserve our close attention, it is equally vital not to neglect infectious disease control in our efforts to prevent chronic illnesses. Not only are infectious disease threats still rife but non-communicable diseases and communicable diseases often fuel each other and require integrated prevention and treatment efforts. The future of health programming, particularly in developing countries, is not necessarily best guided by the epidemiological transition but more accurately by a holistic model that recognizes the key contributions of both communicable and non-communicable diseases to poor health outcomes.

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