“The rapid spread of Dengue could lead to a global pandemic, and so the geographical extent of this spread needs to be assessed and predicted. There are also reasons to suggest that transmission of Dengue from non-human primates in tropical forest cycles is being underestimated.”
Exactly one month ago, on June 7th, PLOS Neglected Tropical Diseases published a research article Worldwide dynamic biogeography of zoonotic and anthroponotic Dengue. The study is the first high-resolution analysis of how the risk of Dengue transmission has been changing geographically since the late 20th century, indicating the virus (DENV) has been making a home in previously low-risk areas, potentially due to global warming and deforestation.
We spoke with the corresponding author Alisa Aliaga-Samanez, who worked alongside Marina Cobos-Mayo, Raimundo Real, Marina Segura, David Romero, Julia E. Fa, and Jesús Olivero, to learn more about the importance of this study and her experience working with GIDEON data.
We got to know GIDEON thanks to an article published in PNAS by Kris A. Murray and colleagues entitled “Global biogeography of human infectious diseases.”
We know that GIDEON is one of the most complete data sources worldwide on zoonoses, so we wanted to use it to build our database. For that reason, the project where I work at the University of Malaga funded our access to GIDEON.
Biogeographical studies, through modeling, applied to pathogens, allow us to understand the distribution of infectious diseases. The occurrence of disease cases is related to social factors but also to environmental variables that determine the degree to which certain environments favor the occurrence of disease, even where it has not been recorded. Thanks to the tool we use in our study, we are able to propose different management strategies depending on which factors favor the risk of transmission in different regions of the world. We took into account three possible biogeographical scenarios related to Dengue transmission risk: (1) zones with favorable conditions for viruses and vectors, (2) favorable conditions for virus only, and (3) favorable conditions for vectors only. Besides, our biogeographical approach helped us to analyze the extent of the areas where non-human primates could be involved in sylvatic Dengue cycles.
We think global warming may be one of the factors that could be favoring vectors to adapt to new environments. A study published by Messina and colleagues in 2019 concluded that the World’s population at risk of Dengue could experience an almost 60% increase by 2080. In addition, they suggested that outbreaks could reach areas in continents such as Australia, Argentina, Japan, eastern China, and southern Europe.
We have seen that governmental bodies such as WHO or CDC rely on scientific studies to manage risk areas, but we feel that this work is being limited in Africa, for example. On the other hand, some diseases already have a vaccine available, such as yellow fever, but its application might not be well managed in some African countries, where large outbreaks occur. In the case of Dengue, a vaccine has already been developed, but it is only licensed for people aged 9-45 years in some countries. The WHO recommends that the vaccine should only be administered to people with confirmed previous Dengue virus infection. As we show in our paper, Dengue is currently spreading together with its vectors. The COVID-19 pandemic should serve to demonstrate that global pandemics are possible and, so, must be prevented.
GIDEON helped us to get quick access to the available information on the disease. This allowed us to build our databases in a short time and to validate our models with recent cases in order to assess the reliability of the tool we use and to predict new areas favorable for new Dengue cases.
Most of the available data on human cases do not differentiate whether they were caused by sylvatic or urban transmission. Some research studies in certain local areas may be able to determine this, but globally there is no such information. Our biogeographic outputs related to Africa and Asia are consistent with the scarce information available and provide the context in which on-the-ground prospections on sylvatic Dengue should be addressed. This is especially important in South America, where sylvatic Dengue has not been detected yet (although the presence of sylvatic Yellow Fever and other evidences are starting to suggest its existence).
We appreciate the great work GIDEON does in collecting data globally. We found the new GIDEON interface very useful. Perhaps it would make it easier in the future, if it is possible, to distinguish between imported and autochthonous cases within the database. It is true that in many cases the database does mention it but not for all countries.
Alisa Aliaga-Samanez has a degree in Biology from the Federico Villarreal University (Peru) and a Master’s degree in Biodiversity and Environment from the University of Malaga (Spain). Currently, she is working at the Animal Biology Department of the University of Malaga, being part of the Biogeography, Diversity and Conservation Group, developing her Ph.D. thesis. The thesis is focused on the study of primate biogeography, applied to conservation and human health. She is currently mapping vector-borne zoonotic diseases through global distribution modeling.
Aliaga uses high-resolution global maps and the most up-to-date databases to analyze geographical changes in the risk of zoonotic disease transmission. In addition, in these analyses, she considers the biogeographical contribution of primates in increasing the risk of transmission. She seeks to determine the potential natural range of endemic and emerging zoonotic diseases in the world, with the aim of suggesting specific management strategies according to the spatial distribution of risk factors.
Click here to read the open-access article: Worldwide dynamic biogeography of zoonotic and anthroponotic Dengue
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