By Cheryl Pellerin
USINFO Staff Writer

This is the first in a series of articles on the U.S. contribution to global disease surveillance.

Washington - Disease outbreaks arise from simple movements: a sick person boards a plane to a far-off place; a virus jumps from a duck to a person, changing itself in the process; land developers clear a forest and microbes there seek new hosts; viruses and bacteria evolve into drug-resistant strains.

Until about 10 years ago, it would have been impossible to recognize a resulting epidemic or pandemic early enough in the event to mitigate its effects. Today, an international network of laboratories and scientists is doing just that, with tools on the ground and in space.

At the core of the network is the U.S. Department of Defense Global Emerging Infections Surveillance and Response System (GEIS), with laboratories in the United States and in Cairo, Egypt; Jakarta, Indonesia; Nairobi, Kenya; Lima, Peru; and Bangkok, Thailand. (See related article.)

“We coordinate global disease surveillance for the Department of Defense,” GEIS director Colonel Loren Erickson said in a May 17 USINFO interview, “and collaborate across the U.S. government with other federal agencies” and with international groups like the World Health Organization (WHO).

EMERGING INFECTIOUS DISEASES

GEIS was created in 1996 by a presidential directive that expanded the role of federal agencies, including the Defense Department, to improve domestic and international infectious disease surveillance, prevention and response.

The directive defined emerging infectious diseases as “new, resurgent or drug-resistant infections for which the incidence in humans has increased within the past two decades or threatens to increase in the near future” that present “one of the most significant health challenges facing the global community.”

Such diseases include HIV/AIDS, now a pandemic; severe acute respiratory syndrome (SARS), which caused a major epidemic in 2002-2003 of more than 8,000 known cases and 774 deaths; and avian influenza, a disease of birds that has infected people, producing 306 human cases and 185 deaths worldwide since 2003. (See related article.)

Disease surveillance begins in hospitals and clinics, where physicians report cases of targeted diseases to public health laboratories.

In the case of avian flu, cases are confirmed by specially equipped laboratories, and epidemiologists investigate key aspects of disease activity - time, location, virus type and disease severity. Analyzing such information allows scientists to predict disease transmission and guides control measures.

Outbreaks of some diseases can be predicted in advance. Beginning in the late 1990s, scientists from NASA’s Goddard Space Flight Center and the Walter Reed Army Institute of Research in Maryland found a way to do this with Rift Valley fever, a viral disease carried by mosquitoes that infects cattle, buffalo, sheep and goats. From those hosts, the virus then can infect people.

According to WHO, Rift Valley fever can cause severe disease in animals and people, leading to high morbidity and mortality.

MONITORING DISEASE FROM SPACE

For about 10 years, through the GEIS program, NASA scientists have been using satellite climate observations - near-real-time vegetation measurements, sea-surface temperatures and more - to monitor rainfall conditions in East Africa that are associated with the outbreak of diseases, including Rift Valley fever.

“These are areas that undergo frequent droughts and flood events,” said Assaf Anyamba, a research scientist with the Goddard Earth Sciences and Technology Center, in a recent USINFO interview. “For example, two years ago there was a huge drought in eastern Africa. This year there are huge floods. These changes in climate are resulting in the emergence of various types of diseases.”

Every month, Anyamba and his colleagues submit disease risk maps based on satellite observations of rainfall and vegetation. Last year, the U.S. National Oceanic and Atmospheric Administration issued an unscheduled advisory about an El Niño weather pattern, indicating that warmer-than-normal sea surface temperatures across the equator could affect global tropical rain patterns.

“When we first saw the El Niño emerging from the Pacific and the Indian Ocean beginning to warm,” Anyamba said, “we issued an early warning. As we began to see the rain, we issued another early warning, showing that the rainfall was on the scale of [a Rift Valley fever outbreak there in] 1997-1998. As the land began to green up, because these areas were very dry, you had conditions that were conducive to the emergence of mosquito vectors [virus carriers] and their propagation.”

In that series of warnings, Anyamba and his colleagues provided the forecast that helped Kenya, Somalia and Tanzania prepare for the Rift Valley fever outbreak that is occurring now, and allowed international partners - WHO, the U.N. Food and Agriculture Organization and others - to help mitigate the outbreak by arriving with personal protective equipment, such as gloves, masks and mosquito nets, to protect against the spike in malaria cases that occurs during flooding rains.

December is a month of sacrifice for Muslim populations in the region, and because blood and tissues from sick animals can infect people who handle them, the government temporarily banned the slaughter of camels, sheep, goats and cattle, saving potentially thousands of lives.

Ten years earlier, during the 1997-1998 outbreak, WHO estimated that there were 89,000 human cases of Rift Valley fever and up to 250 resulting deaths in eastern Kenya and southern Somalia, one of the largest outbreaks of the fever in recorded history.

“The advantage we had this year,” Anyamba said, “is the mechanism in place to do observations. It has lessened the impact in terms of the loss of human lives because we have an early-warning system in place.”

More information about GEIS is available on the Defense Department Web site.