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Murine typhus, an acute zoonotic infection caused by Rickettsia typhi (1), occurs worldwide. It is under-diagnosed and largely underreported because of its nonspecific characteristics and frequently mild course, a lack [...]

To the Editor: Chikungunya virus (CHIKV) first emerged in Indian Ocean islands off the eastern coast of Africa in 2005 and was responsible for large-scale epidemics on the islands of [...]

BackgroundAfter 40 years of limited viral circulation, Reunion Island has since 2018 experienced recurrent dengue outbreaks of increasing intensity and severity.AimWe aimed to report on the epidemiology and characteristics of dengue in Reunion Island between 2018 and 2021.MethodsBetween 2018 and August 2021, we systematically collected data on dengue cases via an automated transmission system between the health authorities and the medical laboratories. We set up additional surveillance systems for dengue-related activity in primary care, in emergency departments and in inpatient departments.ResultsUntil 2020, despite numerous cases, outbreaks had a limited public health impact because of few severe cases, low lethality and no heavy burden for the health care system. In 2021, however, the number of severe cases increased (from 0.4% of all cases in 2018 to 0.8% in 2021), as did the number of paediatric cases (from 8% in 2018 to 15% in 2021) and atypical clinical forms of dengue (108 cases of post-dengue maculopathy). Of note, haemorrhagic forms were rare and multi-organ failure was the most frequent severity throughout the study period. In parallel, the dominant serotype switched from DENV2 to DENV1 in 2020 and DENV1 became the only serotype detected in 2021.ConclusionThese findings indicate that dengue is becoming endemic in Reunion Island. Since comorbidities associated with severity of dengue are common in the population, health authorities should carefully consider the impact of dengue when addressing public health policies.

Murine typhus is a flea-borne zoonotic disease that has been recently reported on Reunion Island, an oceanic volcanic island located in the Indian Ocean. Five years of survey implemented by the regional public health services have highlighted a strong temporal and spatial structure of the disease in humans, with cases mainly reported during the humid season and restricted to the dry southern and western portions of the island. We explored the environmental component of this zoonosis in an attempt to decipher the drivers of disease transmission. To do so, we used data from a previously published study (599 small mammals and 175 Xenopsylla fleas from 29 sampling sites) in order to model the spatial distribution of rat fleas throughout the island. In addition, we carried out a longitudinal sampling of rats and their ectoparasites over a 12 months period in six study sites (564 rats and 496 Xenopsylla fleas) in order to model the temporal dynamics of flea infestation of rats. Generalized Linear Models and Support Vector Machine classifiers were developed to model the Xenopsylla Genus Flea Index (GFI) from climatic and environmental variables. Results showed that the spatial distribution and the temporal dynamics of fleas, estimated through the GFI variations, are both strongly controlled by abiotic factors: rainfall, temperature and land cover. The models allowed linking flea abundance trends with murine typhus incidence rates. Flea infestation in rats peaked at the end of the dry season, corresponding to hot and dry conditions, before dropping sharply. This peak of maximal flea abundance preceded the annual peak of human murine typhus cases by a few weeks. Altogether, presented data raise novel questions regarding the ecology of rat fleas while developed models contribute to the design of control measures adapted to each micro region of the island with the aim of lowering the incidence of flea-borne diseases., Competing Interests: The authors have declared that no competing interests exist.

Introduction: When the first cases of the 2005-2006 chikungunya epidemic struck Reunion Island, local health authorities set up an island-wide operational epidemiologic surveillance system for these infections. This system relied on vector control teams, which conducted active case-finding around the reported cases, and on a sentinel physician network. In addition, in March 2006, the Sephira and Reunion-Telecom companies, in partnership with the Reunion-Mayotte interregional epidemiology bureau (CIRE), developed an innovative system of epidemiologic monitoring by electronic data transmission., Methods: This system relied on the participation of volunteer physicians who transmitted epidemiologic data through the data terminals used for the transmission of electronic treatment forms to the health insurance funds. Using the patient's insurance identification card, each physician provided information about consultations related to chikungunya. This information was transmitted, via the Sephira server in France to Reunion-Telecom, which processed, aggregated and transmitted these data weekly to the CIRE. This network was separate from and independent of the sentinel physician network,, Results: In all, 44 physicians, accounting for 6% of the general practitioners in Reunion, participated in this system, which went into operation during week 14 of 2006. The data collected allowed an assessment of the trends in the epidemic incidence rate by calculating the percentage of consultations related to chikungunya among all consultations (office visits and house calls). For weeks 14-26 of 2006, when the epidemic transmission had spread across the entire island, the Reunion-Telecom health network data proved to be closely correlated with the results of the sentinel physician network surveillance system used to monitor the epidemic trends (correlation coefficient=0.97)., Conclusion: The system provided very encouraging results in monitoring disease time trends in a period of massive epidemic. Its simplicity of use and the speed of data transmission are undeniable assets for its future development. Because it offers the possibility of monitoring other diseases with epidemic potential, such as dengue and influenza, it opens new prospects for infectious disease surveillance.