Historically, infectious diseases have a profound effect on human populations, including their evolution and cultural development. Despite significant advances in medical science, infectious diseases continue to impact human populations in many parts of the world. Reports of disease outbreaks have been more frequent during the past few years. For example, tuberculosis (TB), according to the World Health Organization is now the world-leading killer of adults, 30 million adults are expected to die from TB in the next 10 years. With the spread of HIV, coupled with deterioration of conditions in many cities, not just in developing countries but throughout the developed world as well, and the explosion in international travel, a resurgence of tuberculosis has occurred in Tokyo, New York, London, and other major cities. Eastern Europe and the former Soviet Union have been battling a diphtheria epidemic since 1990. More than 25,000 cases have been reported. Costs from infectious diseases can be high worldwide. The 2003 SARS outbreak costs China and Canada about 1% of their economies.