[Epidemiological surveillance du chikungunya on Reunion Island from 2005 to 2011]. / La surveillance epidémiologique du chikungunya a la Réunion entre 2005 et 2011.

INTRODUCTION: The largest chikungunya epidemic in history hit Reunion Island in 2005/6. At that time, a specific monitoring system was set up. Since the end of the epidemic, this monitoring system has continued to operate and has been enhanced. The main objectives of the system are early detection of any case of chikungunya virus infection and epidemiological monitoring. METHODS: During nonepidemic periods, surveillance is focused on active detection of all cases. During epidemic periods, weekly incidence is estimated using data collected via a sentinel physician network. Occurrence of severe and fatal forms is tracked during all epidemiologic situations. RESULTS: In 2005-2006, the estimated number of symptomatic chikungunya-virus infections diagnosed on Reunion Island was 266 000, i.e., an attack rate of 34%. A total of 222 severe cases and 44 mother-to-child transmissions were recorded. Since the end of the outbreak, two clusters have been detected in the western region of the island in 2010 and 2011. The second cluster was non-negligible since it involved 164 cases including 112 that were biologically confirmed. CONCLUSION: Based on results recorded from 2005 to 2006, the chikungunya monitoring system appears to have good sensitivity and reactivity. Recent detection of two disease clusters confirms the system's efficacy.

Re-emergence of dengue in Reunion, France, January to April 2012.

Since January 2012, 20 autochthonous cases of dengue virus (DENV) infection have been identified in Réunion. The first cases were detected on the western coast, but the two co-circulating viruses (DENV-1 and DENV-3) seemed to have spread later to different cities of the island. There is a non-negligible risk of increase in viral transmission over the following weeks, so health professionals and public health authorities in Réunion are preparing to face a potential epidemic.

Epidemiology of Chikungunya infection on Reunion Island, Mayotte, and neighboring countries.

Since 2004, the frequency of chikungunya virus infections has been increasing in Africa, Indian Ocean islands, and Asia. The epidemic began on the Kenyan coast, and reached the Comoros at the end of 2004 before spreading to the South-western Indian Ocean islands (SWIOI) in 2005 and especially in 2006. The epidemic then spread to Asia where epidemic foci are still active today. This increase also affected temperate zone countries where imported cases were reported, and indigenous transmission was reported in Italy in 2007, and in France (Var) in 2010. This review provides an update on the knowledge gained from monitoring chikungunya infections in SWIOI. Despite significant differences in design and performance, the implementation of surveillance systems has allowed describing the evolution of epidemic waves in the affected areas. Synchronous epidemic waves were observed in SWIOI, despite the differences between the preventive measures locally implemented. Between 2005 and 2007, all SWIOI were in inter-epidemic situation, except for Madagascar where a persistent virus circulation in an endemic-epidemic pattern was observed. In 2009, and in 2010, two moderate indigenous outbreaks were identified on the Reunion Island by the inter-epidemic surveillance system. Strains analyses demonstrated a reintroduction of the virus from Madagascar. These limited outbreaks should be a reminder of the vulnerability of SWIOI to arbovirosis, since the entomological indexes for competent vectors are high and the virus keeps on circulating more or less actively in the area.

[Dengue fever in the Reunion Island and in South Western islands of the Indian Ocean]. / Dengue à la Réunion et dans les îles du sud-ouest de l'océan Indien.

South Western islands of the Indian Ocean are permanently threatened by dengue fever outbreaks. On the Reunion Island, two dengue outbreaks were biologically documented (1977-1978 and 2004). And since July 2004 there has been an inter-epidemic period for the island with sporadic cases and clusters. Between January 1, 2007 and October 5, 2009, the epidemiologic surveillance system detected five confirmed autochthonous cases, five confirmed imported cases (South-East Asia), and 71 probable cases. All the five autochthonous confirmed cases occurred in Saint-Louis during two consecutive clusters. In other South Western islands of the Indian Ocean, several dengue fever outbreaks have been reported. Importation of dengue virus from South-East Asia is a major risk for a new outbreak on the island. The introduction of a new serotype could lead to the emergence of new and severe clinical forms, including dengue hemorrhagic fever.

[Epidemic of influenza A(H1N1) 2009 in Reunion Island: epidemiological data]. / L'épidémie de grippe à virus A(H1N1) 2009 à la Réunion: données épidémiologiques.

In Reunion Island, a French subtropical island located in the southern hemisphere, the monitoring of the epidemiological dynamics of the epidemic linked to the emergence of pandemic virus A(H1N1) 2009 was achieved through the regular influenza surveillance system which has been reinforced on that occasion. It was mainly based on a network of sentinel physicians, combined with virologic monitoring, and on surveillance of severe cases and deaths. The data were analyzed and retroinformation was distributed according to a weekly frequency. The first imported case was confirmed on July 5, 2009 in a traveler arriving from Australia, whereas the first autochthonous cases were reported on July 23. The epidemic peak was reached in five weeks and the duration of the whole epidemic episode was 9 weeks. Pandemic virus has quickly supplanted seasonal viruses that had begun to circulate. The estimated attack rate for symptomatic cases of infection with virus influenza A(H1N1) 2009 was 12.85%. The hospitalization rate was 32 per 10,000 estimated cases, and 24 people had a serious form requiring care in ICU. Among death certificates received at the regional office for health and social affairs, 14 mentioned the influenza, including 7 in whom the pandemic virus has been laboratory confirmed. These deaths occurred in patients significantly younger than usually observed in Reunion Island during the seasonal influenza epidemics. Overall, the epidemic intensity and severity have been similar to those of seasonal influenza in Reunion Island.

[Epidemiological surveillance of leptospirosis on Reunion Island in 2004-2008: possible impact of Chikungunya infection on the case fatality rate of leptospirosis]. / Surveillance épidémiologique de la leptospirose à la Réunion, 2004-2008: possible impact de l'épidémie de chikungunya sur la létalité de la leptospirose.

In 2006, increased mortality due to leptospirosis in Reunion Island had alerted the authorities and justified the conduct of this study in order to update knowledge on the epidemiology of leptospirosis, whereas the latest epidemiological data published on the disease dated back to 2003. This study followed the scheme of a descriptive retrospective survey based on data from reporting and investigation of hospitalized cases of leptospirosis that occurred in Reunion between the 1st January 2004 and 31st December 2008. Data from the National Reference Center (NRC) have also been used. The annual number of reported cases (40 to 50) was stable over the period, which contrasted with the historical decreasing trend of incidence reported by the NRC. The circumstances of exposure were those usually associated with the disease on the island: about 80% of cases were infected between January and June, during the wet season; the main exposure factor identified was the practice of agriculture, declared or not; Leptospira icterohaemorrhagiae remained the most frequently isolated serovar, although regressing. Finally, our study has shown that excess mortality observed in 2006 did not result from an increased incidence but from a rise in the case fatality rate. This could be linked to the outbreak of chikungunya, which peaked in February 2006. In endemic areas of leptospirosis, health professionals should remain aware of the risk of occurrence of fatal cases during arbovirosis outbreaks.

Preliminary analysis of the pandemic H1N1 influenza on Reunion Island (Indian Ocean): surveillance trends (July to mid-September 2009).

First infections with the 2009 pandemic H1N1 influenza virus were identified on Reunion Island in July 2009. By the end of July, sustained community transmission of the virus was established. Pandemic H1N1 influenza activity peaked during week 35 (24 to 30 August), five weeks after the beginning of the epidemic and has been declining since week 36. We report preliminary epidemiological characteristics of the pandemic on Reunion Island in 2009 until week 37 ending September 13.

Sporadic cases of chikungunya, Réunion Island, August 2009.

On 28 August 2009, French authorities reported five cases of chikungunya fever on Reunion Island: three confirmed, one probable, and one suspected case under investigation. All three confirmed patients presented with an acute febrile syndrome, arthralgia, myalgia and cutaneaous rash. All live in the same area on the western side of the island.