Les maladies infectieuses émergentes.

Abstract

Au cours de ce dernier quart de siècle, de nouvelles zoonoses virales sont apparues, telles que le SIDA ou les fièvres hémorragiques. Cette propension des agents pathogènes d’origine animale à infecter les populations humaines n’est pas l’apanage des virus, comme le montre l’encéphalopathie spongiforme bovine. L’émergence de ces maladies nouvelles tient essentiellement aux modifications de l’environnement, imposées par l’homme, et aux changements dans son mode de vie et son comportement. Seules, l’augmentation de la surveillance épidémiologique au niveau mondial, l’amélioration des systèmes de santé publique, l’éducation et la recherche de nouveaux antibiotiques et de nouveaux vaccins nous permettront de lutter efficacement contre la menace sans cesse renouvelée des maladies infectieuses.

New infectious diseases have always been <<emerging>>, but greater prosperity and increased life expectancy led industrialized countries to believe that they were able to protect themselves from infectious diseases. The unexpected appearance of the HIV/AIDS pandemic, together with the identification of new viruses causing fulminating infections, such as haemorrhagic fevers and encephalitis, led to the progressive use of the term <<emerging>> to describe these recently recognized diseases. The term <<re-emerging>> was eventually coined to characterize known pathogens thought to be well controlled or disappearing, at least in industrialized countries, but which made a sudden and unexpected come-back. This has been the case for pathogens causing malaria, tuberculosis, plague, yellow fever and cholera. Major ecological changes closely linked with continued expansion of the human population, the development of international travels, wars and poverty have often led to the emergence of new infectious diseases or to the reemergence of old diseases. Amongst the new diseases, viral haemorrhagic fevers are endemic on every continent. They are caused by a diversity of zoonotic viruses, whose natural hosts have not been fully elucidated, but include rodents, ungulates or monkeys, and can be transmitted by ticks or mosquitoes. Because of the ease of travel, and of the human penetration of rain forests or other ecological niches, we are increasingly vulnerable to these diseases. Evidence is accumulating that HIV is also a zoonotic virus, whose passage from chimpanzees into humans most likely occurred several times within the last century, probably through direct exposure to infected ape blood. A combination of various factors, such as socio-economic and behavioral changes, urbanization, prostitution and the use of nonsterilized needles for parenteral injections, is probably involved in the appearance of the AIDS epidemic in the later part of the century. The identification of virus reservoirs and vectors, and the detection and monitoring of infectious diseases are critical for control and prevention. So is the development of new vaccines and the access to existing vaccines for all.