From an orbit hundreds of miles above Earth, NASA's constellation of climate-research satellites may not be able to spot a flea in the desert Southwest.
But a program that uses space observations to pinpoint the habitats of rodents carrying plague-infected fleas could warn of disease outbreaks in vulnerable areas of New Mexico.
Run by NASA's Applied Sciences Program, the fast-developing tool is mining vegetation, rainfall, temperature and topography data from 14 climate-monitoring satellites to predict and prevent outbreaks of infectious diseases.
The focus is on "vector-borne" diseases spread by rodents, mosquitoes, fleas and ticks. By monitoring climate, precipitation and ground-cover changes that encourage these creatures to thrive, scientists can offer early warnings about potential outbreaks of diseases such as malaria, West Nile virus and bubonic plague.
"This is a huge breakthrough revolution in the field of public health," says program manager John Haynes, who unveiled NASA's infectious-disease-finding abilities for doctors attending the American Society of Tropical Medicine and Hygiene meeting in Philadelphia last month.
Satellites have been used to predict the weather since 1960. Their use in making public-health decisions is only about a decade old.
"There's been a paradigm shift," Haynes says. NASA is reaching out to "front-line troops who are our nation's health defense."
Information from the remote sensors is being shared with the federal Centers for Disease Control and Prevention, the Defense Department, state health agencies, the World Health Organization and foreign governments.
Unlike surveys of patients, which are prone to human error, satellite data "provides a reliable tool for public health that … is not confounded by other factors," says Teresa Fryberger, NASA's Applied Sciences Earth Science Division director.
Among the diseases targeted:
A parasitic disease spread by mosquitoes in tropical climates, malaria is a top concern for military planners. In 2003, one-third of U.S. personnel involved in a peacekeeping mission in Liberia came down with the disease.
By combining ground observations with satellite measures of temperature, rainfall, ground-cover density and soil moisture, NASA and military researchers in Thailand and Indonesia have identified hot spots. Maj. Jittawadee Murphy of the Armed Forces Research Institute of Medical Sciences in Bangkok says in an e-mail: "Each species of mosquitoes prefers different and unique habitat to breed. Therefore we're able to estimate mosquito populations in each terrain, predict disease cases at particular time(s) of the year, and conduct research studies for disease control and prevention at the right place and the right time."
Murphy also said scientists use NASA data to predict outbreaks of scrub typhus, a sometimes fatal disease endemic to Southeast Asia, by locating habitats of chigger mites that spread it.
West Nile virus
NASA's Terrestrial Observation & Prediction System combines satellite imagery and ground-station data to collect, integrate and analyze in nearly real time 30 environmental factors that could contribute to the mosquito-borne disease.
William Reisen, a research entomologist at the Center for Vectorborne Diseases at the University of California-Davis, is lead scientist on a project. He shares data with state public health officials and 63 mosquito-control districts.
"If we could forecast where and when" virus-infected insects would swarm, crews "could adjust their control operations to reduce mosquito abundance and have things in place" before people fall ill, he says.
Endemic to the western USA, especially the Four Corners region of the Southwest (the meeting point of Utah, Colorado, Arizona, and New Mexico), bubonic plague spread by rats and their fleas sickens 10 to 20 people a year.
Because rats tend to breed in canyons, NASA combines topographical data with predictions of rodent food supply and migration patterns to predict the location of outbreaks. It shares the information with the CDC. Early warning is crucial, because the plague's flulike symptoms can lead to misdiagnoses that could prove fatal if antibiotics aren't administered promptly.
NASA satellites also can help distinguish between a naturally caused outbreak and one that might result from bioterrorism.
When an outbreak of Rift Valley Fever killed more than 120 people in Saudi Arabia and Yemen in 2000, U.S. military commanders worried it might have been caused by the release of the fever-causing virus by a terrorist cell.
Using rainfall data from NASA's Tropical Rainfall Measuring Mission satellite and vegetation measurements from the Terra and Aqua satellites, scientists discovered "the heaviest rainfall in that area than they'd had in 30 years." The rain boosted the mosquito population, so "with extremely high likelihood, we determined it was naturally caused," Haynes says.
NASA plans seven more global climate science satellites by 2013, which should expand the number of infectious diseases it can monitor.
One candidate is avian flu, which is spread by waterfowl. The U.S. Agency for International Development already finances programs to tag migratory birds with GPS satellite transmitters to monitor their movement and match their paths with disease outbreaks.
"It's up to us at NASA to use our research ability to determine if there are any environmental observations (that can shed light on) the transmission of this disease," Haynes says.