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Colombia Médica

On-line version ISSN 1657-9534

Colomb. Med. vol.48 no.2 Cali Apr,/June 2017


Letter to Editor

Reflections on Afro-descendant origin and the outcome of dengue fever cases in Colombia

Aura Caterine Rengifo1  , María Alexandra Durán2  , Yamileth Ortíz3  , Jorge Martín Rodriguez4  , Martha Lucía Ospina5 

1 Grupo de Morfología Celular. Instituto Nacional de Salud, Bogotá, Colombia.

2 Red Nacional de laboratorios. Instituto Nacional de Salud. Bogotá, Colombia.

3 Subdirección de Investigación, Científica y Tecnológica. Instituto nacional de Salud. Bogotá, Colombia.

4 Director de Investigación en Salud Pública. Instituto Nacional de Salud. Bogotá, Colombia.

5 Directora del Instituto Nacional de Salud de Colombia. Bogotá, Colombia.

Dear editors, cordial greetings

As a group of researchers and professionals signing this letter to the editors, respectfully, we want to make a series of observations and reflections regarding the article "Afro-Colombian ethnicity, a paradoxical protective factor against dengue" 1, published in your prestigious journal.

We considered that the article in question lightly concludes that the Afro-Colombian population present a lower risk of complications compared to the non-Afro-Colombian population. This situation, besides of not being completely based on data and facts that it describes and analyzes, is an assertion that can be a source of deeply disorientation for the Colombian health services, upon a time these conclusions get disseminated, and it can also mistakenly indicate to Afro-Colombian people that the risk of complications is lower in the presence of a virus causing a dengue disease.

In our point of view, several of the article’s affirmations can be object of xenophobic and exclusive evaluations towards the Afro-Colombian populations, mostly perceived when the authors conclude that in zones or neighborhoods with high number of Afro-Colombian there is a greater incidence of dengue among this population. The authors did not show data or measurements of this condition to identify whether (or not) Afro-descendants were infected at the site of evaluation and whether (or not) they developed the disease, so that these findings should have been assessed more rigorously before making this kind of affirmations and “risky” conclusion.

Although there are characteristics of Afro-descendants that may give to them less susceptibility to severe dengue manifestations, it is already known about the multifactorial pathogenesis of this disease; in which, variables such as environmental factors 2, Age 3, gender 4, different blood types AB versus types A, O and B 5, allele polymorphisms of human leukocyte antigens 6, and factors associated with leakage Vascular…among others, play an important role.

The conditions related to host genetics and environmental factors might predispose to severe forms of the disease, but the important thing is to bear in mind that most of them have been the result of conclusions obtained by studies of association. In addition, recent meta-analysis studies on factors that may influence dengue’s manifestations indicate that malnutrition has an inverse association with dengue shock syndrome and dengue hemorrhagic fever 7,8. We might then, paradoxically, think that “malnutrition offers a kind of protection against the development of the severe form of the disease”. Therefore, being a person of black race does not mean that he/she is protected against some forms of dengue, neither it indicates that it is a risk factor for other ethnic groups 9.

It is also possible that the article is failing to measure or has bias in misclassification, regarding to the auto-recognition for each patient's race 10. A dichotomous classification as Afro-Colombian or non-Afro-Colombian can generate measurement errors; particularly, considering that an Afro descendant patient (mulatto, zambo, mestizo, and others) can be classified as non-Afro-Colombian. Additionally, genetics of their predecessors makes it much vulnerable to possible complications of external origin infectious events. It is possible that of the 402/431 cases of severe dengue cases with complications in non-Afro-Colombians reported by the authors, several of them have genetic elements and traits of Afro-Colombian population, generating a measurement error in which it would be needed to perform Genetic and biological measurements that were not considered.

On the other hand, it is confusing the fact that when comparing with the conclusions obtained by Rojas et al. 1 in relation to the epidemiological reports made by the National Institute of Health (NIH) in 2013, it differs substantially. For example, the NIH reported that the most prevalent provincial o territories (in order of magnitude) with cases of classical dengue and severe dengue are Tolima, Valle, Santander, Norte de Santander and Cundinamarca. In these territories/provinces, (with the exemption of Valle) there are low black race population (11.

Although the authors state that there is no risk of a possible ecological fallacy, it is obvious that most conclusions were obtained with data analysis of population-level records, which exceed individual conclusions 10. To avoid this type of situation, multi-level or multi-step method validations are required to ensure consistency between the two measurement levels.

Finally, it should be considered that dengue is a complex disease in which mechanisms and severe forms of infection have not been fully elucidated, requiring robust and ethical studies to establish new theories about viral pathogenesis, as to avoid making wrong assumptions for the individuals under the study.


1. Rojas-Palacios JH, Alzate A, Martinez-Romero HJ, Concha-Eastman AI. Afro-Colombian ethnicity, a paradoxical protectiva factor against Dengue. Colomb Med (Cali). 2016; 47(3):133-41. [ Links ]

2. Thammapalo S, Chongsuvivatwong V, Geater A, Dueravee M. Environmental factors and incidence of dengue fever and dengue haemorrhagic fever in an urban area, Southern Thailand. Epidemiol Infect. 2008; 136 (1): 135-43. [ Links ]

3. Were F. The dengue situation in Africa. Paediatr Int Child Health. 2012; 32(s1):18-21. [ Links ]

4. Shekhar KC, Huat OL. Epidemiology of dengue/dengue hemorrhagic fever in Malaysia: A retrospective epidemiological study 1973-1987. Part I: dengue hemorrhagic fever. Asia Pac J Publ Health. 1992; 6(2):15-25. [ Links ]

5. Kalayanarooj S, Gibbons RV, Vaughn D, Green S, Nisalak A, Jarman RG, et al. Blood group AB is associated with increased risk for severe dengue disease in secondary infections. J Infect Dis. 2007; 195: 1014-17. [ Links ]

6. Coffey L, Mertens E, Brehin A, FernándezGarcía M, Amara A, Despres PH, et al. Human genetic determinants of dengue virus susceptibility. Microbes Infect. 2009;11:143-156. [ Links ]

7. Trang NT, Long NP, Hue TT, Hung le P, Trung TD, Dinh DN, et al. Association between nutritional status and dengue infection: a systematic review and meta-analysis. BMC Infect Dis. 2016; 16:172. [ Links ]

8. Huy NT, Van Giang T, Thuy DHD, Kikuchi M, Hien TT, Zamora J, et al. Factors Associated with Dengue Shock Syndrome: A Systematic Review and Meta-Analysis. PLoS Negl Trop Dis. 2013;7(9):e2412. [ Links ]

9. Whitehorn J, Farrar J. Dengue. Br Med Bull. 2010; 95 (1): 161-73. [ Links ]

10. Szklo M, Ninegunto J. Epidemiología Intermedia: Conceptos y Aplicaciones. Madrid: Diaz de Santos. 2000. p. 17-151 [ Links ]

11. SIVIGILA. Situación del dengue en Colombia hasta el 16 de febrero de 2013. Disponible en Accessed: Nov 2016. [ Links ]

Received: January 31, 2017; Revised: February 01, 2017; Accepted: February 10, 2017


Authors Response: Reflections on Afro-descendant origin and the outcome of dengue fever cases in Colombia

Jorge Humberto Rojas Palacios1  2  , Alberto Alzate3  , Héctor Jairo Martínez Romero2  4  , Alberto Ignacio Concha Eastman5 

1 Grupo de Epidemiología y Salud Pública, Secretaría de Salud Pública Municipal de Cali, Alcaldía Municipal de Santiago de Cali, Cali Colombia

2 Grupo de Investigación en modelos y métodos matemáticos para el control y vigilancia del dengue, Cali, Colombia

3 Grupo de Investigación en Epidemiología y Servicios (GRIEPIS). Postgrado de Epidemiología, Universidad Libre, Cali, Colombia

4 Departamento de Matemáticas, Universidad del Valle. Cali, Colombia

5 Alcaldía Municipal de Santiago de Cali, Cali, Colombia

Answer letter to the Editor

We have carefully read Rengifo et al.1, views on our research on dengue and ethnicity 2. Most of their observations point to the classification of ethnicity in the study design, in which we recognize a great difficulty to establish the category of Afro-descendant to each one of the individuals. Some proposals to classify that ethnic group in Latin American populations, based on genetic and biological tests, have shown a great miscegenation, which makes classification difficult 3 The method of self-recognition of the ethnicity is imperfect as we see in the methodology of our study; but it is still valid for the scientific community at this time, while other more efficient, reliable and robust methods arise 4,5.

We disagree with the letter correspondents in considering xenophobic any element of this research. The study design considered any risk of discrimination on the grounds that it directly affected the outcome, and that it safeguarded the principle of equity in the selection and evaluation of variables. Significant results were verified by adjusted models that in some cases refuted the original findings (cumulative incidence by age and ethnic origin). Our interpretations of the results also warn of a silent phase of dissemination of the epidemic in communities with a larger Afro-Colombian population, which may require sanitary adjustments to modify the case numbers of dengue and severe dengue.

Finally, we agree on the complexity of the disease and the limitations of ecological studies; but these two arguments do not detract from the value of the conclusions of the study beyond the limitations we recognize in the discussion. Public health research can contribute to better policy decisions in a region by allowing decision-makers to better understand a problem or situation. But defining what decisions authorities should take in health is a responsibility only of decision-makers, in which they have to take into account other aspects, such as social, economic, technical and also reliance on other sciences 6. In this way, our publication does not encompass defining moral and politically convenient decisions.


1. Rengifo AC, Durán MA, Ortíz Y, Rodriguez JM, Ospina ML. Reflections on Afro-descendant origin and the outcome of dengue fever cases in Colombia. Colomb Med (Cali). 2017; 48(2): 98-99. [ Links ]

2. Rojas-Palacios JH, Alzate A, Martinez-Romero HJ, Concha-Eastman AI. Afro-Colombian ethnicity, a paradoxical protectiva factor against Dengue. Colomb Med (Cali). 2016; 47(3):133-41. [ Links ]

3. Wang S, Ray N, Rojas W, Parra MV, Bedoya G, Gallo C, et al. Geographic patterns of genome admixture in Latin American mestizos. PLoS Genet. 2008;4(3): e1000037. [ Links ]

4. Agudelo-Suárez AA, Martínez-Herrera E, Posada-López A, Rocha-Buelvas A. Ethnicity and health in Colombia: what do self-perceived health indicators tell us? Ethn Dis. 2016; 26(2): 147-56. [ Links ]

5. Larifla L, Beaney KE, Foucan L, Bangou J, Michel CT, Martino J, et al. Influence of genetic risk factors on coronary heart disease occurrence in Afro-Caribbeans. Can J Cardiol. 2016; 32(8): 978-85. [ Links ]

6. Feldhay R. The fragile boundary between the political and the academic. Israel Studies Review. 2013; 28(1):1-7. [ Links ]

Carta al editor

Respuesta: Reflecciones sobre el origen Afro-descendiente y el resultado de casos de dengue en Colombia

Respuesta carta al Editor

Hemos leído con atención las apreciaciones de Rengifo et al.1, respecto a nuestra investigación sobre dengue y etnia 2. La mayoría de sus observaciones apuntan hacia la clasificación de etnia en el diseño del estudio; donde reconocemos una gran dificultad para establecer la categoría de afrodescendiente a cada uno de los individuos. Algunas propuestas para clasificar la etnia en poblaciones latinoamericanas con base en pruebas genéticas y biológicas han mostrado un gran mestizaje que dificulta la clasificación 3. El método de la auto reconocimiento de la etnia es imperfecto como lo advertimos en la metodología de nuestro estudio; pero válido para la comunidad científica en este momento, mientras se propongan otros métodos eficientes, más confiables y robustos 4,5.

Diferimos con los corresponsales de la carta en considerar xenofóbico cualquier elemento de la investigación. En e l diseño del estudio consideró cualquier riesgo de discriminación por considerar que afectaba directamente el resultado y se resguardo el principio de equidad en la selección y evaluación de las variables. Los resultados significativos fueron comprobados por modelos ajustados que en algunos casos refutaron los hallazgos originales (incidencia acumulada por edad y origen étnico). Nuestras interpretaciones de los resultados también alertan de una fase silenciosa de diseminación de la epidemia en comunas con mayor población afrocolombiana que puede requerir ajustes sanitarios para modificar las cifras de caso de dengue y dengue grave.

Por último, coincidimos en la complejidad de la enfermedad y las limitaciones de los estudios ecológicos; pero, estos dos argumentos no restan el valor de las conclusiones del estudio mas alla de las limitaciones que reconocemos en la discusión. Las investigaciones en salud pública pueden contribuir a que se tomen mejores decisiones políticas en una región, porque le permite a los gobernantes entender mejor un problema o una situación. Pero, definir que decisiones debe tomar una autoridad en salud es una responsabilidad únicamente del gobernante, donde tiene que tener en cuenta otros aspectos, como los sociales, económicos, técnicos y además apoyarse en otras ciencias 6. De este modo, nuestra publicación no alcanza a definir sobre las decisiones morales y políticamente convenientes.

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