world. Chloroquine was historically the primary drug for treating malaria, but its widespread use has led to increasing microbial resistance. Scientists have now identified a particular type of mutation at a specific location on a single gene as being critical in the development of resistance, and efforts are now under way to develop new drugs that target this resistance mechanism. Praziquantel is the only drug now available to treat schistosomiasis. Since the drug has been in use for more than two decades, concerns are mounting that the parasitic worms that transmit the disease from snails to humans are beginning to become resistant. Among the immediate needs, praziquantel’s effectiveness can be prolonged by more selective use, with treatment targeted only to those people at greatest risk for heavy infection and morbidity, as well as by the use of integrated disease management practices, such as snail control, health education, and improved sanitation. At the same time, new drug development needs to continue in anticipation of the eventual failure of praziquantel efficacy.

Influenza is a global threat to health. Vaccines represent the first line of defense against the flu, with a new vaccine being developed and distributed each year in response to the changing genetic composition of the causative virus. Still, vaccines are not a total answer, and several classes of antiviral drugs have been developed to treat infected individuals. Two antivirals— amantadine and rimantadine—have been around since the 1960s. Although effective in some circumstances, both types of drugs suffer from drug-resistance problems. Another family of newer drugs, called neuraminidase inhibitors, shows even more promise, as these formulations appear to pose a reduced risk of triggering resistance. A major problem, however, is that the pharmaceutical companies that produce these newer drugs are not making enough doses to cover medical needs in the event—certain to happen at some point—that a highly modified and virulent form of the influenza virus emerges from the animal world and spreads among the human population worldwide.

Adding to concerns about antimicrobial resistance is the possibility that terrorists or a rogue nation might use “bioweapons” to expose large numbers of people to genetically engineered drug-resistant pathogens in order to trigger large-scale disease outbreaks. This scenario was brought into sharp perspective in autumn 2001 by the intentional distribution through the U.S. mail of envelopes containing spores of Bacillus anthracis. One issue considered during this session involved the effects of exposure to both anthrax and ionizing radiation at the same time, conditions that military personnel, in particular, might someday face. Based on a recent study in mice, scientists have been able to identify some fundamental factors that contribute to increased susceptibility to bacterial infections in general, and to B. anthracis in particular, after ionizing radiation, as well as to make some general

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