Paul-Louis Simond and yellow fever.

P.L. SIMOND participated in the Pasteur institute mission sent to Rio de Ja neiro from 1901 to 1905 to investigate yellow fever and was to make an impo rtant contribution to the knowledge of the disease. At that time, the aetio logic agent of yellow fever was still unknown, and its transmission by mosq uitoes was controversial. Several authors had observed apparent differences in the susceptibility to the illness between African and European populati ons, Otherwise the soundness of epidemic control measures then being admini stered was often called into question. As such, many points needed to be de finitely clarified. During the four years they spent in Brazil, the Pasteur Institute scientist s - and particularly SIMOND - achieved important results. They confirmed th e viral aetiology of yellow fever were able to define several pathological aspects of the disease and conduct various serotherapeutic tests. The role of Aedes aegypti (known at the time as Stegomyia fasciata) was also confirm ed and the bionomics of the mosquito began to be studied. This research lai d he ground for classical measures of controling the vector and preventing outbreak; of the disease. Furthermore, MARCHOUX and SIMOND observed the ver tical transmission of yellow fever virus in Ae. aegypti; this phenomenon of major epidemiological importance remained controversial until it was confi rmed in the field as recently as 1997. The French scientists were also able to specify many aspects of the epidemiology of yellow fever particularly i ts apparent low pathogenicity in young children - a possible explanation fo r the fact that local residents of endemic zones often had a certain level of immunity as a result of benign infection contracted in childhood. P.L. SIMOND later spent several months in Martinique where he set up a succ essful yellow fever vector control programme. Clearly SIMOND, who had alrea dy acquired much expertise in the epidemiology of vector-borne diseases, pl ayed a key role in the success of the mission sent by Institute Pasteur to Brazil, and, more generally in he scientific advances of yellow fever preve ntion.