Travelers' health.

Over the last century and a half, the world's population has grown from one billion to almost six billion, and the time required to circumnavi-gate the globe has decreased from 365 days to fewer than 3. Currently, 1.4 million persons travel internationally by air every day. The speed and volume of international travel are cited by the Institute of Medicine as principal factors contributing to the global emergence of infectious diseases. This panel assessed the effect of travel on emerging infections from the perspectives of both industrialized (Jay Keystone) and developing countries (David Shlim), discussed the role of vaccination in preventing travel-related infections (Robert Steffen), and explored unique health issues associated with travel into space In the past decade, international travel has grown dramatically to the point where more than 500 million travelers cross international borders annually by commercial aircraft alone. Mass migrations of refugees, workers, and displaced persons have led to a steady growth of urban centers at the expense of rural areas. These population movements have been ideal conduits for the global spread of new and reemerging infectious diseases. Virtually any place in the world can be reached within 36 hours, less than the incubation period for most infectious diseases. Infectious agents can spread from person to person directly or to vectors at the traveler's destination. Vehicles of human transport , such as aircraft and ships, also transport the infectious agent and its vector. In addition, mass migrations have facilitated the rapid and immediate spread of communicable disease among refugees and displaced persons. If travelers are responsible for the spread of infectious agents, they are also ideal sentinels for the arrival of an infectious agent in a new community. In 1969, the first documented outbreak of Lassa fever was noted among American missionaries in Lagos, Nigeria. In 1992, two Peace Corps volunteers contracted neuroschistosomiasis; a subsequent investigation confirmed that Lake Malawi was an important source for the transmission of Schistosoma haematobium. More recently, chlo-roquine-resistant Plasmodium vivax was documented for the first time in North Africa in U.S. Army troops returning from Somalia. These and many other examples show that travel is instrumental in the spread of new and reemerging infectious diseases. As international travel grows by more than 10% per year and major population shifts continue because of political, economic, and social instability, public health agencies will have to focus their infectious disease surveillance programs on travelers, migrants, …