Emerging diseases and ecosystem instability: new threats to public health.

Ecologists have begun to describe an environmental distress syndrome, whereby widespread loss of top predators and harsh environmental conditions are encouraging the selection of opportunistic pests and pathogens across a wide taxonomic range of plants and animals. Environmental change and pollutants stress individuals and populations, and this may be reflected in the global resurgence of infectious disease as these stresses cascade through the community assemblages of species. In 1993, the sudden appearance of a virulent, rodent-borne hantavirus in the arid US Southwest accompanied anomalous weather patterns, and a novel Vibrio cholerae variant (O139 Bengal) emerged in Asia where marine ecosystems are experiencing a pandemic of coastal algal blooms, apparently harboring and amplifying the agent. This paper suggests a framework for integrating the surveillance of health outcomes and key reservoir and vector species, with ecological and climatic monitoring.