Recent studies have shown that genetic variants, responsible for the different human response when facing an infectious risk, concerned the genes of proteins involved in either recognition of the infectious agent, in the inflammatory cascade, or in the coagulation process. For example, some studies clearly demonstrated that if a twin was affected by an infectious disease, the risk of infection by the same agent for the other twin was significantly higher in homozygote than in heterozygote twins. In Caucasians, a punctual mutation of the TLR2 cytosol was proved to block the response to bacterial lipoproteins and to some Gram positive bacteria and could be responsible for a greater susceptibility to septic shock. Several polymorphisms of the tlr4 gene have been involved in the onset of septic shock in postsurgery infection due to Gram(-) bacilli. Paradoxically, these variants seemed to protect against legionellosis. In pediatrics, polymorphisms of tlr4 were also clearly identified as risk factors for meningococcemia of severe bronchiolitis due to the respiratory syncytial virus (RSV) in children under 2 years of age. A polymorphism of the TLR5 receptor gene, which creates a stop codon and which is responsible for a nonfunctionality of the receptor was associated with the onset of severe legionellosis. Analysing the functions of these genetic polymorphisms in the onset of sepsis will open the way to a lot of research on specific treatments focused on genetic abnormalities.