ASSOCIATION AFFAIRS Global Climate and Infectious Disease : The Cholera Paradigm

Historically, infectious diseases have had 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. Emerging diseases are considered to be those infections that either are newly appearing in the population or are rapidly increasing in incidence or expanding in geographic range (1). Emergence of disease is not a simple phenomenon, mainly because infectious diseases are dynamic. Most new infections are not caused by truly new pathogens but are microorganisms (viruses, bacteria, fungi, protozoa, and helminths) that find a new way to enter a susceptible host and are newly recognized because of recently developed, sensitive techniques. Human activities drive emergence of disease and a variety of social, economic, political, climatic, technological, and environmental factors can shape the pattern of a disease and influence its emergence in.to populations. For example, travel affects emergence of disease (2), and human migrations have been the main source of epidemics throughout history. Trade caravans, religious pilgrimages, and military campaigns facilitated the spread of plague, smallpox, and cholera. G lobal travel is a fact of modem life and, equally so, the continued evolution of microorganisms; therefore, new infections will continue to emerge, and known infections will change in distribution, frequency, and severity. Reports of disease outbreaks have been more frequent during the past few years. For example, two malaria cases were recently reported in New York and traced to local mosquitoes. These cases demonstrate that the potential exists for reintroduction of malaria into areas where it is no longer endemic, such as the United States. Malaria is an old disease with the potential of reemerging as a new disease, especially in association with climate change. Tuberculosis (TB), according to the World Health Organization, is now the world's leading killer of adults; 30 million