Satellites Used to Help Predict Deadly Disease Outbreaks

Renee Juhans/Dave Steitz

Headquarters, Washington, DC

(Phone: 202/358-1712/1730)

John Bluck

Ames Research Center, Moffett Field, CA

(Phone: 650/604-5026)

Steve Berberich

University of Maryland Biotechnology Institute, Baltimore, MD

(Phone: 410/385-6315)

RELEASE: 00-73

NASA is providing new insights from space that may help
health officials predict outbreaks of deadly water-borne cholera,
a bacterial infection of the small intestine that can be fatal to
humans.

Scientists have learned how to use satellites to track blooms
of tiny floating plant and animal plankton that carry cholera
bacteria by using satellite data on ocean temperatures, sea height
and other climate variables. The work is described in a recent
paper co-authored by University of Maryland Biotechnology
Institute (UMBI) and NASA researchers that appeared in the
Proceedings of the National Academy of Sciences.

“These experiments fulfill our hypothesis that cholera is
associated with environmental conditions,” said Dr. Rita Colwell,
founder and former president of UMBI, and now Director of the
National Science Foundation. She is presently on leave of absence
from the University of Maryland, and is co-author of the cholera-
tracking project paper.

The authors found that rising sea temperatures and ocean
height near the coast of Bangladesh in the Bay of Bengal from 1992
to 1995 often preceded sudden growth, or “blooms,” of plankton and
outbreaks of cholera. Similar application of risk analysis
developed by NASA using satellite data has also been used in the
study of diseases such as malaria, Lyme disease and Rift Valley
fever.

“When such a model for Bangladesh is extended to the global
scale, it may serve as an early warning system, enabling effective
deployment of resources to minimize or prevent cholera epidemics
in cholera-endemic regions,” according to Brad Lobitz, principal
author of the paper and a contract scientist at NASA’s Ames
Research Center, located in California’s Silicon Valley. The
scientists correlated years of hospital cholera records from
Bangladesh with sea temperature and ocean height data that came
from a variety of satellites and surface observations.

Satellites not only can measure water temperature and ocean
height, but also can measure colors that indicate plankton and
chlorophyll over a large sea area, Lobitz explained. Tracking sea
temperatures from ships and by other direct measurements is too
expensive to be practical, he added.

Cholera may result in extreme diarrhea, vomiting and loss of
water. Victims can die within a day or so unless body fluids are
replenished quickly. The seventh cholera pandemic began in 1961
and now affects six continents, according to the paper. A
pandemic is an epidemic that occurs over a large region.

Sea height is important because tides reach further inland to
affect more people who may drink or bathe in brackish water
carrying cholera. “Bangladesh is very low and flat, and tidal
effects are felt almost half way up into the country,” said co-
author Louisa Beck of California State University at Monterey Bay
and a resident scientist at Ames.

“The 1992-to-1995 study is important because all the remote
sensing satellite data are in the public domain,” Beck said. “The
main point is that we obtained the data at no cost because it is
available on the web.”

“In most years Bangladesh has two cholera outbreaks,” Lobitz
said. “These are in the spring and fall.” The authors discovered
that the sea surface temperatures show an annual cycle similar to
the cholera-case data.

The effort was a cooperative project between NASA’s Office of
Life and Microgravity Sciences and Applications and UMBI. The
study was also supported by grants from the National Institutes of
Health and the Environmental Protection Agency. The other authors
include Byron Wood, Ames; Anwar Huq, UMBI; and George Fuchs and A.
S. G. Faruque, the International Centre for Diarrhoeal Disease
Research, Bangladesh. More information about the cholera-tracking
project is on the Internet at:

http://geo.arc.nasa.gov/sge/health/projects/cholera/cholera.html

The researchers used data from three Earth-observing
satellites in the study: a National Oceanographic and Atmospheric
Administration weather satellite, the SeaWiFS instrument aboard
the SeaStar (OrbView-2) satellite, and the U.S.- French
TOPEX/Poseidon oceanography satellite. Data from SeaWiFS and
TOPEX/Poseidon are provided through NASA’s Office of Earth
Sciences, which is dedicated to studying how natural and human-
induced changes affect the Earth’s global environment.

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