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Tackling El Niño’s Influence on Diseases Through GIS Mapping

Drs. Lee and Ramirez reviewing a map of disease risk in Peru during El Nino.

February 8, 2019

In 2015, Peru was hit with a severe malaria outbreak along with food shortages, floods and droughts — all of which were triggered by an El Niño event. On average, Peru has the second highest rate of malaria in South America with over 55,000 confirmed cases during the 2015 event.

Because of El Niño’s effects on short-term climate and weather patterns, it’s not surprising that this phenomenon also influences infectious diseases in affected areas. 

Peru is considered ground-zero for El Niño events to unfold; thus, a UNC geographer and her colleagues decided to study how El Niño affected numerous, climate-sensitive diseases there in 1998 using Geographical Information Systems (GIS) mapping technology. 

Drs. Ramirez and Lee
Ramírez (left) and Lee (right).

The chosen year and location are important for their research because it was considered one of the most powerful events to occur at that time. They discovered connections between the flooding and torrential rainfall that occurred with the 1998 El Niño event and outbreaks of diseases in the Piura, Peru, area.

“The main goal of the study was to develop ways to think about and visualize the occurrence of multiple infectious disease outbreaks that emerge during extreme weather or climatic events,” said Ivan Ramírez, Ph.D., a geography and environmental sciences instructor at the University of Colorado, Denver.

Ramírez worked with University of Northern Colorado Assistant Professor in Geography & GIS Jieun Lee, Ph.D., to fully map the concentrated instances (known as hot spots) of the diseases over time in that area of Peru. They tracked diseases that included cholera, malaria, conjunctivitis (or pink eye), pneumonia, and three others categorized as acute, diarrheal diseases.

“An El Niño event has been forecasted this year, and it means that it should be developing this spring, and so this kind of research is very relevant and timely,” said Ramírez. “If we can find out where the best places to target with prevention and intervention when the event happens, then it can help public health authorities as well as provide insight to those in disaster management and development.”

Map from their research showing hot spots of disease risk during the 1998 El Nino event in Peru.
Above: The maps demonstrate the evolving patterns of ecosyndemic (multi-infectious disease risk) from January to March and an overall seasonal pattern (Jan. to Mar.) in 1998. The red indicates high risk, which concentrates in the west, and the blue indicates low risk in the east. (Image from published research in International Journal of Environmental Research and Public Health, Vol. 15, Issue 12).

Geography and GIS can complement and strengthen other sciences by examining relationships between specific phenomena and provide a visual picture of what’s going on. For example, Lee is teaching a course at UNC about crime mapping that uses GIS applications to identify patterns of criminal activities and explore related environmental factors to certain activities.

“Things that happen around us have locational elements,” said Lee. “Because they’re happening somewhere, we can use the information about the location to create a map, and GIS effectively visualizes where things happen and gives us an understanding as to why they happen in specific places and times, if the data allows.”

Listen to the full interview with Ramírez and Lee about their GIS research on multi-disease risk in Peru during the 1998 El Niño event: 

Follow along with the podcast's transcript below:

Hi, I’m Katie Corder, the creative content producer at the University of Northern Colorado. I sat down with Jieun Lee, who is an assistant professor of geography and geographic information systems, or GIS, at UNC, as well as Ivan Ramírez, a geography and environmental sciences instructor at the University of Colorado, Denver, to discuss their published research on studying the 1998 El Niño event in northern, coastal Peru and its influence on the spread of seven diseases.

The year and location are very important for their maps since Peru is considered ground zero for El Niño, and 1998 was one of the strongest El Niño years observed. By using GIS techniques, they were able to better understand the high and low levels of these spreading diseases in Peru. Their findings can assist Peruvian public health officials and those in disaster management and response to better intervene and prepare for risk of disease spread in future El Niño events.

In this podcast, Dr. Lee and Dr. Ramírez go into more detail about the importance of using GIS to map disease spread during El Niño in Peru, how they conducted their research and how GIS can be used to give further insights into different disciplines, such as crime mapping.


Lee: We studied how El Niño, an unusual weather event in Peru, South America, affects the local environment and public health. Particularly tried to understand how many infections and how these infections concentrate in places using cool maps. Because everything happens in a place, and if we know the location of it, you can map it!

Could you describe your research on mapping the multi-disease risk during El Niño, and what do you mean by “multi-disease risk?”

Ramírez: We refer to this type of public health phenomena or problem as “ecosyndemic.” Basically, what we did was examine seven water-related diseases in northern, coastal Peru in a place called Piura. In early 1998, and 1998 is very important because there was a very strong El Niño, or climatic event, that occurred then, and what we did was explore two ways, or two methodologies, that we can map such phenomena.

Multi-disease just means rather than focusing on one disease, we’re starting now to look at interactions between diseases, and, as geographers, we’re looking at more in the context of place.

“Ecosyndemic”: Can you break that apart for us?

Ramírez: If your immune system is weakened, then you’re more susceptible to other infections. The concept was actually developed so that you could look at these disease interactions, which have some biological grounding, but also, the fact that they might be also embedded within a wider social context: why are people exposed? Why are certain people exposed? Why is it spreading within certain populations? It has this strong social context. We kind of touched on that in the study but we were interested in looking at ‘Well, what are the geographic boundaries of syndemics, and how are they manifested when it comes to the context of environmental change?’

The types of diseases that were looked at?

Ramírez: What’s interesting about all of these is they’re water-related, so they all have some kind of water connection. We looked at cholera, we looked at two types of malaria, conjunctivitis, we looked at other diarrheal diseases that weren’t cholera, pneumonia as well as other respiratory diseases that weren’t pneumonia, so it was a set of seven diseases.

Can you describe how you mapped the multi-disease risk, and what software/program and techniques?

Lee: To map the multi-disease risk we used ArcGIS, GIS is software, GIS here is short for geographic information systems that was developed and is now widely used to capture, store, manipulate, analyze and manage geospatial and geographic data. So, when we organized the data for disease for this study and other factors with locational information, then we can then easily create maps that show spatial patterns to see if there are spatial clusters, there are concentrating in certain areas, or how widely the patterns are dispersed. Then, we can explore the potential links or relationships between the spatial patterns and other contextual factors, such as vulnerability of the population, environmental elements, even the extreme events. In this research, besides the individual disease incidents maps, so an individual map represents an individual disease, we also used IDW, which is Inverse Distance Weighing and tabulation techniques to create a smooth surface. For the multi-disease risk using this index, we created a composite index. Another GIS technique we incorporate in this research was hot-spot analysis, which uses a statistical treatment to detect where spatial clusters of high value, which means hot spot or great concentration, or low value with the other side of the value that other concentrates occurred.

Can you explain in non-technical terms how an El Niño event occurs, and what’s to be expected when an El Niño is predicted?

Ramírez: Cold water in the east rises to the surface, it gets pulled to the surface and gets pulled by the winds towards the west, and you have a pile up of warm water, and when it’s exposed to the sun it gets warm. And with that warm water moving towards the west, you got moisture moving in that direction, too, and you have drier conditions off the coast of western South America. Once an El Niño starts developing, what we might tend to see is that the winds weaken. And if we say the winds are weakening, then those winds aren’t pulling the currents anymore towards the west, and this occurs over several months. Once those waters are not being pulled towards the west anymore, they start to shift back. Once they start shifting back, it’s really this warm mass of water that starts moving towards South America, and when those warm waters hit the coast of South America, the surface temperature at the ocean rise, and so, El Niño then with this warm water invasion disrupts this cold water. Basically, the Pacific Ocean is pretty big … it’s basically the atmosphere and the ocean, or the air and the sea, interacting with one another, speaking to one another, influencing one another, and these large-scale changes across the Pacific are now linked to other weather patterns around the planet. Of course, most immediate are along the Equator, but it goes beyond that, as well. And those changes, locally and regionally and globally, impact disease pathogens, and they impact what kind of weather or climate-related hazards we might experience: floods and droughts are the simplest ones to think about.

Can you describe how this research is influential to future research and/or policy planning? How would someone who makes policies and is trying to rectify these issues?

Ramírez: Right now, we have an El Niño event that’s been forecasted. It means that it should be developing this spring. If we can find ways to visualize multiple diseases, but even then, moving further to looking at disease and social problems today, and find out where might be the best place to target interventions where you might have greater concentrations of more diseases than usual. It can help public health authorities. I think it might also provide some insight to those who are looking at disaster management and development, as well, as indicators of vulnerability in these places at certain times. GIS enables you to visualize these patterns of change and when you’re better identifying or locating you can have a more precise location in place, that also depends on the data. The index that we created, can also tell us what communities are most sensitive, so if we look at vulnerability we might also look at which communities are most sensitive to these extreme events and when, which would enable public health authorities to act.

Can you describe how geography and GIS are connected to other sciences, such as in this research? 

Lee: Geography, by all means, is very interdisciplinary and complimentary to other disciplines in sciences by bringing special perspectives. And investigating the relationship between specific phenomena and a special context that creates really the wholesome big picture. Things that happened around us have locational elements. They’re happening somewhere, then we can use the information about the location to create a map. Specifically, GIS takes a role in effectively visualizing where things happen and understanding why they happen in the specific places and time, if the data allows. For example, I teach a course here at UNC that’s crime mapping that introduces GIS applications to our students to identify spatial patterns of criminal activities and explore related environmental factors to certain activities.

I think those are all the questions I have! Thank you so much for speaking to me, and congrats on the publication.

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