This article is based on a document published in May 1999 by the Directorate General for Health and intended for physicians practicing in regions affected by Hemorrhagic Fever with Renal Syndrome (HFRS) in France. Hemorrhagic fever with renal syndrome is a disease caused by viruses of the Hantavirus family (primarily the Puumala virus in France), whose natural hosts are rodents. These rodents carry the infection asymptomatically and excrete large quantities of the virus in their urine, feces, or saliva. Humans become infected through the respiratory tract by inhaling the virus present in rodent excreta or, more rarely, through bites. The natural host of the Puumala virus is the red-backed vole, which lives in forests and sometimes in nearby buildings. Hantavirus infection was serologically confirmed for the first time in France in 1982. Since then, approximately 800 cases have been diagnosed. Most of the diagnosed cases have occurred in the northeastern quarter of the country in the form of epidemic outbreaks every three years.