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Chances of worldwide plagues increasing, scientists say

STANFORD -- Population growth is adding to the threat of massive epidemics, two Stanford scientists told a meeting at the Beijer Institute of Ecological Economics of the Royal Swedish Academy of Sciences in Stockholm on Monday, Sept. 11.

Speaking on "Development, Global Change and the Epidemiological Environment," ecologists Gretchen C. Daily and Paul R. Ehrlich described the many changes, both positive and negative, that "enlarging the scale of the human enterprise has produced in the epidemiological environment."

That environment consists of all the conditions that influence the interactions between human beings and disease agents such as bacteria, viruses and malaria parasites. Development changes some of those conditions for the better, by improving water supplies, sanitation and health care. But it also can help create large cities with gigantic slums that promote close contact, unsanitary conditions, promiscuous behavior and drug use that have led to them being called "graveyards of humanity," the scientists said.

"Large human populations can maintain many infectious diseases that small ones cannot, and large ones also are more likely to be invaded by pathogens previously restricted to monkeys, mice or other non-human animals," Daily and Ehrlich said.

"Today's populations also contain many hungry people, and hunger reduces the efficiency of the body's immune defenses. There also are escalating numbers of people infected with the HIV virus [which causes AIDS], which attacks the immune system. Thus, humanity now amounts to a vast monoculture, increasingly ripe for invasion by rapidly evolving germs. To make matters worse, high-speed transport systems now can spread epidemics around the world in a matter of days," they said.

The Stanford scientists found two trends especially threatening. One is the increasing contact of growing human populations with animal reservoirs of potentially lethal pathogens. "AIDS is likely just to represent the tip of that epidemic iceberg," they said.

The second is the rapid, near catastrophic evolution of resistance to antibiotics and other drugs by bacteria, malaria organisms and other dangerous parasites of human beings. Many strains of bacteria, notably some of the kind that cause tuberculosis (which Daily and Ehrlich call humanity's most deadly enemy), are now resistant to essentially all antibiotics. Some strains of malaria in Southeast Asia already are resistant to anti-malarial drugs so new that they have yet to be approved for sale in the United States, they said.

"This return to the pre-antibiotic era is rooted in the ignorance of evolution that pervades both the medical community and the general public," they said. "It is in part a lethal legacy of the success of the creationists. To this day, the United States still allows the feeding of antibiotics in gigantic quantities to farm animals -- a sort of social suicide that helps disarm us in our war against bacteria."

Further, the misuse of insecticides, both in attempts to control disease-carrying insects and in the process of the intensification of agriculture, has led to the evolution of resistant insect vectors -- particularly the Anopheles mosquitoes that transmit malaria, Daily and Ehrlich said. "The evolution of resistance is simply the inevitable consequence of the misuse of our chemical weapons, something evolutionists have warned against for decades."

Various aspects of "global change" also can cause the deterioration of the epidemiological environment. An example is global warming, which has the potential of spreading tropical diseases such as malaria into what are now the temperate zones.

The Stanford team recommended various strategies for improving the epidemiological environment. "The most important is to bring the growth of the human population to a halt as quickly as is humanely possible, and then lower the birth rate below the death rate to initiate a gradual decline," they said. "Not only does the size of that population in itself constitute a degrading of the epidemiological environment, but overpopulation is a major cause of other changes, such as rapid urbanization and agricultural intensification, which also degrade it."

They recommended that much more effort be put into disease warning networks, medical infrastructure, national vaccination programs, integrated management of resistance, upgrading of water and sanitary systems and dwellings, and a general emphasis on disease prevention rather than treatment.

"These steps will demand a substantial effort from society, and getting them implemented constitutes a gigantic challenge to physicians, ecologists, economists, political scientists, sociologists, sanitary engineers and others involved professionally in the maintenance of public health. At the same time, this combination of tasks could provide an unprecedented opportunity for interdisciplinary cooperation," they said.

Daily and Ehrlich said that many of the ways of improving the epidemiological environment would involve increasing equity between sexes, races, regions and nations.

"Giving people significantly more equality of opportunity also would amount to a giant step to solving the population-food-environment predicament, as well as many other social problems. By working for equity, one is simultaneously brightening the human future."


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