Tracking Disease Outbreaks From Outer Space

By Roland Piquepaille

Forecasting the emergence of an infectious disease by coupling local data, such as the ecosystem parameters and disease data, with images from satellites is not a new idea, but the technology is here and works, says this article from RedNova. The approach mixes data from high-tech environmental satellites with old-fashioned, "khaki shorts and dusty boots" fieldwork. NASA is setting up a satellite-based malaria pilot study in the Mewat region of India. The goal is give warnings of high disease risk in a specific area up to a month in advance in order to prepare vaccination programs and save people and animals.

Ronald Welch of NASA's Global Hydrology and Climate Center in Huntsville, Alabama, is one of the scientists working to develop such an early warning system.

First, Welch and other scientists visit places with disease outbreaks.

Then they scrutinize satellite images to learn how disease-friendly conditions look from space. The satellites can then watch for those conditions over an entire region, country, or even continent as they silently slide across the sky once a day, every day.

Here is such an image from Baja California taken by a NASA satellite (Credit: NASA).

Let's look at one current project.

In India, for example, where Welch is doing research, health officials are talking about setting up a satellite-based malaria early warning system for the whole country. In coordination with mathematician Jia Li of the University of Alabama at Huntsville and India's Malaria Research Center, Welch is hoping to do a pilot study in Mewat, a predominantly rural area of India south of New Delhi. The area is home to more than 700,000 people living in 491 villages and 5 towns, yet is only about two-thirds the size of Rhode Island.

"We expect to be able to give warnings of high disease risk for a given village or area up to a month in advance," Welch says. "These 'red flags' will let health officials focus their vaccination programs, mosquito spraying, and other disease-fighting efforts in the areas that need them most, perhaps preventing an outbreak before it happens."

How does this work?

Documenting some factors, such as soil type and local bucket-leaving habits, requires initial groundwork by researchers in the field, Welch notes. This information is plugged into a computerized mapping system called a Geographical Information Systems database (GIS).

Fieldwork is also required to characterize how the local species of mosquito behaves. Does it bite people indoors or outdoors or both? Other factors, like the locations of cattle pastures and human dwellings, are inputted into the GIS map based on ultra-high resolution satellite images.

Then region-wide variables like temperature, rainfall, vegetation types, and soil moisture are derived from medium-resolution satellite data.

Scientists feed all of this information into a computer simulation that runs on top of a digital map of the landscape. Sophisticated mathematical algorithms chew on all these factors and spit out an estimate of outbreak risk.

Using this kind of method has already be successful. Here is an example.

A joint NASA Ames / University of California at Davis study achieved a 90% success rate in identifying which rice fields in central California would breed large numbers of mosquitoes and which would breed fewer, based on Landsat data.

So maybe one day, the outbreaks of Dengue or West Nile fevers which kill thousands of people and seem to come from nowhere, will be a thing from the past.

Source: Patrick L. Barry, Science@NASA, March 12, 2004, via RedNova