GLOBAL CHANGE AND EMERGING INFECTIOUS DISEASES

Abstract

Over the past 20 yr we have witnessed epizootics and epidemics involving several pathogenic diseases representing global threats to animal and human health. In the past 5 yr alone epidemiologists and public health workers have been alerted on the ProMed computer site (http://www.promedmail.org) to many human and animal diseases that were transported from one country to another. These included African trypanosomiasis, bovine spongiform encephalopathy (BSE), bovine tuberculosis, brucellosis, campylobacteriosis, cholera, Crimea–Congo hemorrhagic fever, cyclosporiasis, dengue, diphtheria, dracunculus, heartwater, human immunodeficiency virus (HIV) infections, hepatitis types A, B, and E, infectious bovine rhinotracheitis (IBR), influenza A, Japanese encephalitis, Lassa fever, legionellosis, malaria, Newcastle disease, paratyphoid, plague, rabies, Ross River virus infection, shigellosis, trichinellosis, tularemia, typhoid, West Nile fever virus, yellow fever, and yersiniosis. Primarily parasitic diseases, but also a few major diseases caused by other infectious agents, are presented as examples of emerging diseases in the following discussion. Many of these infectious agents and others are vectorborne and ultimately depend for transmission on climatic conditions that are becoming more favorable for the survival of the vectors. The earth’s climate is continually changing. The warming trend of the past 250–300 yr has seen average temperatures approach those of the Medieval Warm Period around the end of the 12th century. Although industrial pollutants were thought to contribute to global cooling recorded in the 1940s through the 1970s, increased atmospheric carbon dioxide and other gases are thought to contribute to a greenhouse effect resulting in the present global warming trend. The past 16 mo have been the warmest in recorded history, and continued warming is forecast. Discussions of the impact of global warming on emerging infectious disease frequently include those diseases associated with tropical climate, such as malaria. Some predictions warn that warmer temperatures will facilitate the spread of malaria and other tropical diseases to Europe and North America, ignoring historical evidence that malaria was once endemic in many temperate regions and that epidemics reached as far as the Arctic Circle. Although the disease is no longer present in most of these areas, the same mosquito vectors remain in many of them, suggesting that temperature is but 1 of many factors influencing disease transmission.