THE INFECTIOUS THREAT

This opening century will appear as both “the golden age of genetics and the dark age of infectious diseases” (Tibayrenc, 2001a). On the battlefront of infectious diseases, the situation is more than just a concern, due to the threat of emerging and reemerging infectious diseases (ERID). In developing countries, infectious diseases still are the main demographic regulating factor. In particular, Africa is more than ever afflicted with sleeping sickness, malaria, bilharziosis, and other major parasitoses. The three “diseases of poverty,” namely malaria, tuberculosis, and AIDS, have become the top priority of the World Health Organization. The industrial world has not been spared. In France, 12,000 people die every year of nosocomial infections. In New York City, 25% of the Mycobacterium tuberculosis strains are resistant to antibiotics.

ENVIRONMENTAL AND BIOLOGICAL FACTORS

Transmission and severity of infectious diseases are the result of a complex interplay between environmental and biological (built-in) parameters. There is no doubt that environmental factors play a major role in the present resurgence of infectious diseases, through climatic changes, massive migrations, economic inequalities, and political instability. However, even in acting on these environmental factors, control is more efficient when sophisticated knowledge of the biology of the disease under survey is available. For example, in Latin America, Chagas disease is a parasitic disease caused by the flagellate Trypanosoma cruzi and transmitted by triatomine bugs (hematophagous tree bugs).