[Genetic control of infectious diseases: from Mendel's laws to exome sequencing]

About one-quarter of deaths worldwide (nearly 13 million per year) are still directly related to infectious diseases. Many new infections have emerged since the end of the 20th century and others will continue to do so. Human beings, like other animals, are not all equal with respect to their susceptibility to infection. Since the 1930s, numerous epidemiological studies have shown that host genetic factors play a major role in susceptibility and resistance to infections. Studies of Mendelian genetics and genetic epidemiology based on association studies, now using high-speed typing of anonymous polymorphic markers, can detect genes or loci that influence an individual's response to a particular germ. Different cases of susceptibility or resistance to viral, bacterial, fungal and parasitic infections will be used to illustrate the importance of genetic factors in the diagnosis of clinical manifestations and their prevention, characterization of host immune responses, and their influence on evolutionary biology. With different phenotypes associated with genetic polymorphisms, and new genomic techniques, the genetics of infectious diseases is entering a new era, raising questions of medical practice, ethics, and public and industrial policies.