Ever since human migrations began, germs have traveled with people and created health hazards for other communities. In an interconnected world, diseases such as HIV/AIDS and SARS bring about challenges unforeseen prior to the age of air travel. But international cooperation through agencies such as the World Health Organization also allows for quicker response times and collective responses to global health threats. Meanwhile, however, large pharmaceutical companies seeking to maximize profit see little potential in developing vaccines or treatments for diseases that mainly afflict people in poor, developing countries, contributing to another level of global inequality made more visible through increased media exposure and travel opportunities. The following articles have been assembled to shed light on these and other related issues.