[Marseilles, the Indian Ocean and Chikungunya virus].

In recent decades Marseilles, through immigration, has become the largest Comorian city outside the archipelago. It is also home to a faculty of medicine that has made infectious diseases one of its fields of excellence. During the last two years, Marseilles has spearheaded the metropolitan French response to the Chikungunya crisis in the Indian Ocean region, and especially in the Reunion Island and Mayotte. Laveran military teaching hospital (Hôpital d'instruction des armées, HIA) has managed one of the largest metropolitan cohorts. Its teams have also reported the broad clinical spectrum of the disease in its later stages, and especially the high incidence of incapacitating tenosynovitis and distal arthritis, as well as the occurrence of a transient acrosyndrome during the second and third months in nearly one-quarter of patients. Importantly, they have also identified a mixed cryoglobulin in more than 90% of patients, the level of which matches clinical symptoms and is sensitive to systemic steroid therapy. This discovery opens the way to a better understanding of the pathophysiology of this viral disease. The Tropical Virology laboratory of the Tropical Medicine Institute of the Army health service (IMTSSA), which has close links with the national references center (CNRS) arbovirus laboratory, has developed new diagnostic tools, notably based on RT-PCR. Together with national reference center (CNRS), the laboratory produces and supplies antigens for Chikungunya serological tests in metropolitan France and overseas. It has taken into account the presence of cryoglobulins, which can lead to false-negative results in infected patients, and has considerably increased the diagnostic yield of serological techniques. The laboratory's fundamental research focuses on genomic characterization of viral variants isolated from humans and from the vector, and also on viral protease expression, for functional studies and antiviral candidate drug selection. The laboratory also collaborates with clinical teams in Reunion and metropolitan France working on humoral and cellular immune responses and on the different clinical forms of the disease. The Epidemiology and Public Health Department of IMTSSA conducted an epidemiological study of all gendarmes working in Reunion at the end of the epidemic (June 2006). This study, done in partnership with the tropical virology laboratory and CNRS, is helping to complete the clinical description of the epidemic, in an unbiased population. In 2007, it will form the basis for a prospective cohort study in which these patients will be monitored for several years to better document the chronic phase of the disease in a population with excellent healthcare access. Finally, the department has provided the civil authorities with advice and support in disease-control operations in Reunion. Communication played an important role in the management of this crisis, showing how crucial it now is for healthcare professionals to develop relevant skills. The Army Health Service in Maarseilles was never isolated from its university partners, as witnessed by clinical collaboration between Laveran HIA and CHU Nord (a Marseilles teaching hospital) and by virological cooperation between the IMTSSA and Etablissement français du sang (EFS) laboratories. This experience is highly encouraging with respect to the creation in Marseilles of a healthcare research network (RTRS) devoted to tropical and emerging infectious diseases.