Chances of Worldwide Plagues Increasing, Scientists Say

November 1, 1995

Population growth is adding to the threat of massive epidemics, two Stanford scientists told a meeting at the Beijer Institute of

Population growth is adding to the threat of massive epidemics,two Stanford scientists told a meeting at the Beijer Instituteof Ecological Economics of the Royal Swedish Academy of Sciencesin Stockholm recently.

Speaking on "Development, Global Change, and the EpidemiologicalEnvironment," ecologists Gretchen C. Daily and Paul R. Ehrlichdescribed the many changes, both positive and negative, that "enlargingthe scale of the human enterprise has produced in the epidemiologicalenvironment."

Development changes some of those conditions for the better, byimproving water supplies, sanitation, and health care. But italso can help create large cities with gigantic slums that promoteclose contact, unsanitary conditions, promiscuous behavior, anddrug use that have led to them being called "graveyards ofhumanity," the scientists said.

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

"Today's populations also contain many hungry people, andhunger reduces the efficiency of the body's immune defenses. Therealso are escalating numbers of people infected with the HIV virus.Thus, humanity now amounts to a vast monoculture, increasinglyripe for invasion by rapidly evolving germs. To make matters worse,high-speed transport systems now can spread epidemics around theworld in a matter of days," they said.

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

The second is the rapid, near catastrophic evolution of resistanceto antibiotics and other drugs by bacteria, malaria organisms,and other dangerous parasites of human beings. Many strains ofbacteria, notably some of the kind that cause tuberculosis arenow resistant to essentially all antibiotics. Some strains ofmalaria in Southeast Asia already are resistant to anti-malarialdrugs so new that they have yet to be approved for sale in theUnited States, they said.

"This return to the preantibiotic era is rooted in the ignoranceof evolution that pervades both the medical community and thegeneral public," they said. "To this day, the UnitedStates still allows the feeding of antibiotics in gigantic quantitiesto farm animals--a sort of social suicide that helps disarm usin our war against bacteria."

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

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

The Stanford team recommended various strategies for improvingthe epidemiological environment. "The most important is tobring the growth of the human population to a halt as quicklyas is humanely possible, and then lower the birth rate below thedeath rate to initiate a gradual decline," they said. "Notonly does the size of that population in itself constitute a degradingof the epidemiological environment, but overpopulation is a majorcause of other changes, such as rapid urbanization and agriculturalintensification, which also degrade it."

They recommended that much more effort be put into disease warningnetworks, medical infrastructure, national vaccination programs,integrated management of resistance, upgrading of water and sanitarysystems and dwellings, and a general emphasis on disease preventionrather than treatment.

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