[Traps in infectious serology].

The role of serology in infectious disease diagnosis is highlighted by HIV and viral hepatitis diagnosis developed since the 80's. However, long before these recent developments serum reactivity played its role in diagnosing, active or previous severe bacterial infection in diseases such as typhoid fever (Widal), brucellosis (Wright test), syphilis (VDRL, Wassermann test), typhus (Weil-Felix test) etc. From early infection to immunity, serology analyzes the patient's immunological memory enabling the fight against infections. The resulting information depends on the type of pathogen, the site of infection, the host and the stage of disease. Together with the direct tests for the detection of pathogens, serological tests form the basis of microbiological diagnosis. To better understand the utility of serology, we will provide an overview and show its pitfalls.