Resurgent and emergent disease in a changing world.

Emerging infectious diseases pose important public health problems for both the developed and developing world. Many new or previously unrecognized bacterial, fungal, viral, and parasitic diseases have emerged within the past two decades. At the same time, many once-controlled infections have re-emerged or become resistant to antimicrobial therapy. This emergence is the result of changes in society, technology, the environment, and the microbes themselves, and these changes have had often unpredictable consequences. Important factors influencing emergence include changes in human demographics and behaviour, changes in technology and industry, changes in economic development and land use, increasing and rapid international travel and commerce, microbial adaptation and change, and the breakdown of public health measures. Addressing emerging infectious diseases will require international and interdisciplinary partnerships to build an appropriate infrastructure to detect and respond to these often unanticipated threats to health.