Experts in biological warfare addressing the annual meeting of the American Association for the Advancement of Science here point to the threat of new strains of bacteria and viruses developed by the former Soviet Union as an example.

``Proliferation of bioweapons technology from these facilities is still a concern,'' said Kathleen Vogel, a Cornell University researcher who has visited some of the weapons plants. Among the possible contents: novel strains of smallpox, anthrax and plague developed to be resistant or impervious to existing vaccines or antibiotics.

Biomedical ethicists worry not only about biological warfare, but also the biological damage that genetically unique organisms might wreak on plants and animals unprepared for them by evolution.

``Even if you try your best not to do harm, sometimes by accident, you do,'' said Stanford University Medical Center researcher Margaret Cho during a symposium on the implications of synthesizing new life forms.

She cited the experience several years ago of Australian scientists who attempted to alter the mousepox virus by adding a gene for mouse interleukin-4, a key immune system cell.

The new strain unexpectedly proved deadly in mice that had previously been resistant to the virus, and even a vaccination against the virus was only partially protective. The researchers delayed publishing their work in part due to concern it might provide a blueprint for terrorists.

Jonathan Moreno, a biomedical ethicist at the University of Virginia, said the threat of ethnically or even more narrowly targeted gene modifications is ominous. ``There is emerging international concern about the possibilities of ethnic warfare using targeted biological weapons,'' Moreno said.

``It is already known that the old apartheid government in South Africa was conducting research for the possible development of biological agents that could be used against the black population. There have also been allegations that Israel has shown an interest in these kind of targeted bioweapons,'' he added.

Harvard University's Matthew Meselson, a molecular biologist and scholar of biological warfare, worries that ``biotechnology will profoundly alter the nature of weaponry and the context in which it is employed.''

He argues that biotech may not only present new ways to kill, but also to manipulate the processes of ``cognition, development, reproduction and inheritance'' and provide ``unprecedented opportunities for violence, coercion, repression or subjugation,'' he told a symposium on biological warfare threats.

Moreno noted that ``it might take decades to realize'' that an attack directed at, say, birth rates or infant mortality of a certain ethnic group had even occurred. ``By that point, a population of people might be seriously diminished.''

Stephen Morse, a public health expert at Columbia University School of Medicine in New York, said, ``There is a great potential for danger from altered strains or even existing strains in bioweapons. But at the same time, there's great hope from biotechnology for dealing with these problems.''

He cited an array of new instruments being developed by the Pentagon that will allow rapid detection and identification of biological agents in the field. These range from germ ``breathalyzers'' to detect what bacteria might be in a soldier's lungs, to miniature mass spectrometers that could identify one germ from tens of thousands.

``I understand the concern about developing new life forms that can be self-replicating with some minimal number of genes,'' said J. Craig Venter, CEO of the genetic sequencing giant Celera, Inc. ``But our ability to quickly screen and identify genetic code should be a great deterrent to any development of new biological warfare pathogens.

``A few years ago, it took labs working for the FBI three days to determine if a threat of an anthrax release in Nevada was real. Now, it would take us less than two hours to do the sequencing,'' Venter said.

Frankengene warfare or terrorism aside, Stanford's Cho also expressed concern about how the way we view life and various life forms might be changed as genes are mixed and matched to make species more useful to humans.

``How many human genes can you add to a monkey before it becomes something you would call human?'' she asked.

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