Global Disease Hotspots 2.0

What drives pandemics? Where will the next one start? And if we know, what can be done to stop it in its tracks?

It was the desire to answer these questions which motivated EcoHealth Alliance’s scientists to create the first ever global emerging disease hotspots map in 2008. Looking at incidents of disease spillover from wildlife to humans, the team then mapped out where these diseases were first identified in an attempt to glean where major future disease events might emerge.

EcoHealth Alliance's new hotspots map

Published Tuesday in Nature Communications, Hotspots 2.0 is a vastly improved update of EcoHealth Alliance’s original map. It takes more variables into account, like wildlife diversity and/or local environment such as climate or terrain. The result is more refined. The map’s biggest takeaway is that it shows, for the first time, that global disease emergence is linked directly to human-induced drivers like land-use change and interactions between humans and wildlife in highly biodiverse regions of the world.

“This work allows us to state, unequivocally, that human behavior on a planet-wide scale creates opportunity for disease to emerge and spread and drives pandemic risk,” EcoHealth Alliance President Dr. Peter Daszak said of the map and its corresponding paper, Global hotspots and correlates of emerging zoonotic diseases, which he co-authored. “Risk comes not only from known pathogens, but also the estimated 1.5 million+ unknown viruses which lurk in biodiverse regions. The brightest areas on our map are the places researchers should be headed to stop the next pandemic before is starts.”

As you can see, the map identifies parts of South and Southeast Asia, West and Central Africa, and Latin America as having the highest potential for disease spillover. Places like Bangladesh, India, and China are the brightest, indicating highest risk. That is for several reasons, first of all these are some of the fastest growing countries worldwide; Bangladesh is currently one of the most densely populated countries in the world. These nations are also heavily forested–India and China–being two of the ten most forested areas in the world–and in a lot of cases, that forest is being razed to extend urban centers or further agricultural production.

Thailand Macaques

As urban environments continue to encroach on traditionally forested areas, animals like these macaques in Thailand have adapted to live alongside humans, leading to more interaction between the two (Photo: EcoHealth Alliance)

It is conditions like these that create high potential for disease to spill from wildlife populations into humans (or vice versa, though the hotspots map only tracks spread of disease in one way). Zoonotic diseases which emerged in Southeast Asia and have jumped to humans include SARS, bird flus, and Nipah virus.

But Hotspots 2.0 is not cause for panic. Instead, it should serve as a roadmap for researchers to determine in which areas they can do the most good. As work like the Global Virome Project continues–aiming to discover and map the world’s unknown pathogens–it is in these hotspots regions where they are most likely to do the most good. For virus hunters, searching for a 20 nanometer (0.0000008 inches) cell on 196.9 million square miles of Earth makes for a pretty fantastic haystack. Thanks to EcoHealth Alliance’s hotspots map, those scientists have better insight into where they should begin.

The original hotspots maps from 2008

Disease spillovers from animals to people are rare events. To catch one where it happens, when it happens is very difficult. Some people don’t show symptoms when infected, and when they do they are ill for only a brief window of time. Some diseases have such general symptoms that they are usually mistaken for other diseases or never get addressed in a clinical context. Being proactive is critical.

“If we had been looking in the Congo—at the populations of apes and humans that lived there—it's possible we would have been in a better position to know about HIV before it went pandemic,” says Toph Allen, EcoHealth Alliance’s Director of Data Science and an author of the paper. “It’s about moving where you’re looking earlier on in the process of emergence.”

One of the reasons the West African Ebola outbreak got so much press is the nightmarish quality of its symptoms. A disease that only gave people mild fevers would hardly have garnered the same level of coverage or hysteria that Ebola did. Because of that, many of these zoonotic spillovers go unnoticed and unreported. The updated hotspots map allows us to focus our energies on places where we're most likely to catch those elusive spillovers. This map’s findings are the but the first steps on a path that leads out of the pandemic era we inhabit.

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