Beyond divisive dichotomies in disease classification
Authors: Felicia Marie Knaul, Octavio Gómez-Dantés, Afsan Bhadelia, Julio Frenk
Journal: The Lancet Global Health (2017)

The divide between communicable and so-called non-communicable diseases (NCDs) is a pervasive, false dichotomy1Frenk J Gómez-Dantés O False dichotomies in global health: the need for integrative thinking.Lancet. 2017; 389: 667-670Summary Full Text Full Text PDF PubMed Scopus (21) Google Scholar of global health. We contribute to the debate on renaming NCDs2Allen LN Feigl AB What's in a name? A call to reframe noncommunicable diseases.Lancet Glob Health. 2017; 5: e129-e130Summary Full Text Full Text PDF PubMed Scopus (42) Google Scholar by proposing an integrating framework that considers both the nature of the disease and the characteristics of the required systemic response. In contrast to other renaming suggestions3Allen LN Feigl AB Reframing non-communicable diseases as socially transmitted conditions.Lancet Glob Health. 2017; 5: e644-e646Summary Full Text Full Text PDF PubMed Scopus (46) Google Scholar which tend to focus on dichotomy, we propose a framework that accounts for systemic responses to coexisting epidemiological profiles, comorbidities in patients, and sustained rather than episodic care. Infections and NCDs were assumed to be unrelated, biologically or otherwise, which resulted in the opposing concepts of communicable versus non-communicable diseases. Scientific progress has, however, revived intellectual debate around the classification of diseases, questioned the distinct nature of infections and NCDs, and shown that most diseases have multiple causes. Infections are not essentially discrete biological events or exclusive to the initial stages of health transition, but are part of a complex biological continuum and shifting epidemiological pattern.4Frenk J Bobadilla JL Sepúlveda J López-Cervantes M Health transition in middle-income countries: new challenges for health care.Health Pol Plan. 1989; 4: 29-39Crossref Scopus (221) Google Scholar Many NCDs have an infectious origin. A fifth of cancers are the result of chronic infections caused by pathogens such as HIV and hepatitis B or hepatitis C virus,5WHOAbout two out of five cancers can be prevented. World Health Organization, Geneva2010http://www.who.int/mediacentre/multimedia/podcasts/2010/cancer_day_20100204/en/Google Scholar, 6American Cancer SocietyCan infections cause cancer?.https://www.cancer.org/cancer/cancer-causes/infectious-agents/infections-that-can-lead-to-cancer/intro.htmlDate: 2016Google Scholar and bacterial and parasitic diseases catalyse NCDs, such as rheumatic heart disease and Chagas cardiomyopathy. The dimension of space, especially as it relates to disease transmission, has often determined global health priorities. Literary accounts of disease dramatise the fear of contagion—eg, Edgar Allan Poe's The Masque of Red Death, Albert Camus's The Plague, or Gabriel García Márquez' Love in the Time of Cholera. Fear of the spread of communicable diseases across national borders generates political urgency.7Horton R Offline: NCDs—why are we failing?.Lancet. 2017; 390: 346Summary Full Text Full Text PDF PubMed Scopus (34) Google Scholar Yet, space becomes relevant even for NCDs because living conditions and environments are social determinants of health.8WHOSocial determinants of mental health. World Health Organization, Geneva2014http://apps.who.int/iris/bitstream/10665/112828/1/9789241506809_eng.pdfGoogle Scholar, 9Singh GK Siahpush M Kogan MD Neighborhood socioeconomic conditions, built environments, and childhood obesity.Health Aff (Millwood). 2010; 29: 503-512Crossref PubMed Scopus (210) Google Scholar The classification of diseases according to a single cause has reduced the scope of prevention, control, and treatment. Most health conditions are the product of multiple, interacting genetic, behavioural, environmental, and socioeconomic factors. In the 1950s, René Dubos wrote “The search for the cause may be a hopeless pursuit because most disease states are the indirect outcome of a constellation of circumstances rather than a direct result of single determinant factors.”10Dubos R Mirage of health. Utopias, progress, and biological change. Harper Colophon Books, New York1979: 102Google Scholar Classifying diseases on the basis of their duration has mistakenly equated the term communicable with acute, and non-communicable with chronic. Although many communicable diseases are acute, some are chronic, such as HIV. Additionally, several acute infections generate long-term sequelae, and some NCDs are characterised by acute exacerbations of underlying longer-term illnesses, such as asthma or depression. Rather than a dichotomy, we propose a dynamic, nuanced classification framework that combines the disease duration and the multicausal transmission mechanism (table). The latter is crucial from an epidemiological point of view, whereas the disease duration is central in designing health-system responses. Time is a continuous variable; however, a widely shared convention is to characterise a disease as either of short or long duration, and the nature of the required health-system response tends to be sufficiently different to justify categorising diseases as either acute or chronic.TableTypology of disease by duration and mode of transmissionCommunicable or associated with infectionNon-communicableChronicCommunicable chronic diseases (CCDs): cancers associated with infections or parasitic diseases (eg, Kaposi sarcoma, lymphoma); chronic infections (eg, tuberculosis, HIV/AIDS); acute infections or parasitic diseases with chronic sequelae (eg, polio, measles)Non-communicable chronic diseases (NCDs): Cancers (eg, breast or lung); cardiac and pulmonary diseases (eg, congestive heart failure or hypertension); other chronic diseases with acute exacerbations (eg, asthma and depression)AcuteCommunicable acute diseases (CADs): most common infections (eg, infectious diarrhoeal disease, acute respiratory infections, or malaria)Non-communicable acute diseases (NADs): cancers (eg, acute myelogenous or lymphoblastic leukaemia); cardiac diseases (eg, acute myocardial infarction)Proposed framework for the classification of diseases with examples. Adapted from 11Knaul FM Alleyne G Piot P et al.Health system strengthening and cancer: a diagonal response to the challenge of chronicity.in: Knaul FM Gralow JR Atun R Bhadelia A Closing the cancer divide: an equity imperative. Harvard Global Equity Initiative, Cambridge, MA2012: 95-122Google Scholar, with permission from the Presidents and Fellows of Harvard College. Open table in a new tab Proposed framework for the classification of diseases with examples. Adapted from 11Knaul FM Alleyne G Piot P et al.Health system strengthening and cancer: a diagonal response to the challenge of chronicity.in: Knaul FM Gralow JR Atun R Bhadelia A Closing the cancer divide: an equity imperative. Harvard Global Equity Initiative, Cambridge, MA2012: 95-122Google Scholar, with permission from the Presidents and Fellows of Harvard College. Adopting two dimensions to stratify diseases generates a fourfold typology: communicable chronic diseases (CCDs), communicable acute diseases (CADs), non-communicable chronic diseases (NCDs), and non-communicable acute diseases (NADs). Retaining the abbreviations of these diseases preserves the known categorisation and acronym, but now the second letter refers to the crucial issue of chronicity. This framework integrates epidemiological and health-system issues, emphasises the complex and diverse origin of diseases, accommodates for change from scientific discovery and technological progress, and offers a set of acronyms that expresses the complexity of disease patterns.12Aluwihare A Renaming the NCDs.Bull World Health Organ. 2002; 80: 173PubMed Google Scholar, 13Allen LN Feigl AB Reframing non-communicable diseases as socially transmitted conditions.Lancet Glob Health. 2017; 5: e644-e646Summary Full Text Full Text PDF PubMed Scopus (2) Google Scholar, 14Rigby M Renaming non-communicable diseases.Lancet Glob Health. 2017; 5: e653Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar, 15Lincoln P Renaming non-communicable diseases.Lancet Glob Health. 2017; 5: e654Summary Full Text Full Text PDF PubMed Scopus (6) Google Scholar, 16Kozelka EE Jenkins JH Renaming non-communicable diseases.Lancet Glob Health. 2017; 5: e655Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar, 17Zou G Decoster K McPake B Witter S Renaming non-communicable diseases.Lancet Glob Health. 2017; 5: e656Summary Full Text Full Text PDF PubMed Scopus (8) Google Scholar Consider the advantages of this classification when applied to HIV/AIDS. From an epidemiological control point of view, the fact that HIV/AIDS is communicable is hugely relevant, but from a health-system perspective, chronicity is key as patients live with multiple, acute complications and comorbidities.18WHOWorld health report 2010. Health systems financing: the path to universal coverage. World Health Organization, Geneva2010Google Scholar, 19Coleman K Austin BT Brach C Wagner EH Evidence on the chronic care model in the new millennium.Health Aff (Millwood). 2009; 28: 75-85Crossref PubMed Scopus (1072) Google Scholar The debate on nomenclature offers a unique opportunity to secure a more balanced and integrated approach to setting global health priorities. This framework can supersede simple dichotomies and strengthen our ability to address the complex health challenges facing us at the present time. We declare no competing interests.