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Perspectives in Health Magazine
The Magazine of the Pan American Health Organization
Special Centennial Edition
Volume 7, Number 2, 2002

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Hurrying Toward Disaster?
by C. J. Peters

As human impact on the earth increases exponentially, the chances for unpleasant surprises from the microbial world will also grow.

 Illustration A young man--a trained athlete in the prime of life--lies on his sofa with aches that penetrate to his bones. He turns up the air conditioner as his fever drenches him in sweat. He drinks a little water but has no appetite after vomiting throughout the night. He feels as bad as he has ever felt in his life. The weight of his lethargy presses him down into the couch. Soon, he begins to feel short of breath. In a few hours, he will go to the hospital, but it won t matter. Even state-of- the-art intensive care cannot revive his failing heart, suction his edematous lungs fast enough or replace the fluid with sufficient oxygen for him to breathe. Within 48 hours, the young man will have drowned in his own blood plasma.

It may sound like a fiction writer's overheated imagination, but this is what really happened in the southwestern United States in 1993. Cases of the "mystery disease" piled up. Newspapers alarmingly reported the "experts stumped." Local physicians quickly realized they were up against something beyond their knowledge, and even the accumulated scientific wisdom at the nearby university proved little help. State public health authorities were unable to solve the problem, and when officials of the U.S. national Centers for Disease Control and Prevention were called in, they had nothing to offer but an investigation. Finally, after a concerted effort, authorities discovered the root of the malady was a virus carried by a local rodent, which showed no signs of illness itself. This new hantavirus caused a new disease, hantavirus pulmonary syndrome, or HPS, which to this day we do not know how to prevent or treat.

Given the growth of global travel, changes in the earth's ecology and natural viral mutation, one country's emerging disease is potentially another's next epidemic.

The story of HPS exemplifies our increasing awareness of threats from the microbial world and our halting efforts to confront them. The dangers are not just a media invention; they are real and significant. The main components of the problem are the emergence of "new" organisms, shifting tactics of known infectious agents and the growing resistance of pathogens to existing antimicrobial drugs.

Although the threat of emerging and reemerging infectious diseases is greatest in the developing countries of the tropics, countries with higher incomes face the danger as well. Two other "new" hantaviruses were discovered after people died in small, poor Amerindian communities in Paraguay and in one of the most expensive neighborhoods on Long Island, New York, in the United States.

While the industrialized world has more resources to prepare for these threats, its impressive health progress over the last century has led to widespread complacency about diseases that seem to affect primarily the world's poor. Yet with the growth of global travel, changes in the earth's ecology and natural viral mutation, one country's emerging disease is potentially another's next epidemic. What's more, the factors that favor emerging diseases are also present--in some cases even accentuated--in the developed world.

"New," but not so new
The evolution of pathogens is measured in centuries or millennia, so truly new organisms do not simply burst upon the scene from nothing. Usually, they have undergone quiet periods of development in nonhuman hosts, then changes in ecology or human society lead to their emergence as killers and their recognition by medical science.

Such was the story of the rodent-borne hantaviruses: they have been parasites of native rodents in the Americas for at least 30 million years, but in 1993, climate changes caused by the El Niño southern oscillation led to increased breeding and rapid growth of rodent populations in the southwestern United States and a subsequent spillover of the virus into human populations.

Cases of the disease had occurred but gone unrecognized for many years until more accurate tests for viruses allowed us to define a "new" disease that had not been diagnosed previously. More important, scientists found that in the Americas, more than 20 different viruses could cause this new clinical disease. Each virus is carried by a different rodent species, with distinct epidemiological patterns dependent on the host species and its interaction with people. HPS has now been recognized in most of the countries of the Americas and is considered a significant threat to the Region's public health.

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