Dengue in New Caledonia: Knowledge and Gaps.

Arboviruses are viruses transmitted to humans by the bite of infected mosquito vectors. Over the last decade, arbovirus circulation has increasingly been detected in New Caledonia (NC), a French island territory located in the subtropical Pacific region. Reliable epidemiological, entomological, virological and climate data have been collected in NC over the last decade. Here, we describe these data and how they inform arboviruses' epidemiological profile. We pinpoint areas which remain to be investigated to fully understand the peculiar epidemiological profile of arbovirus circulation in NC. Further, we discuss the advantages of conducting studies on arboviruses dynamics in NC. Overall, we show that conclusions drawn from observations conducted in NC may inform epidemiological risk assessments elsewhere and may be vital to guide surveillance and response, both in New Caledonia and beyond.

Measles during arbovirus outbreak: a diagnostic challenge.

INTRODUCTION: Dengue fever is a major public health problem in New Caledonia, like in many Pacific Islands Countries and territories. In 2017 New Caledonia faced multiple circulations of arboviruses with a major outbreak of dengue and a co-circulating Zika virus. New Caledonia is considered as a non-endemic territory for measles since the mid 1990's. CASE PRESENTATION: A 41-year-old male presented fever, headache, sinusitis and exanthematous maculopapular rash. A clinical diagnosis of arbovirus was first suspected due to the local epidemic context. A few days later the patient was admitted to the main hospital. The real time RT-PCR for dengue and Zika virus were negative on the first blood sample. A drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome and other infectious diseases including measles were then suspected. ELISA tests for measles were positive for IgM and equivocal for IgG. A throat swab was immediately shipped to a reference laboratory for measles nucleic acid testing. After a week, the patient recovered and the presence of measles RNA was confirmed. No secondary cases were reported among contacts of the patient and the source of his infection could not be ascertained. CONCLUSION: Diagnosis of measles during an arbovirus outbreak in a country where measles disease is rare can be a pitfall for healthcare professionals. The introduction of measles via returned travellers or tourists from areas where measles remains endemic is a real threat to countries with high vaccine coverage.

Zika virus infection as an unexpected finding in a Leptospirosis patient.

INTRODUCTION: Areas where leptospirosis and arboviruses are endemic largely overlap in the tropics. However, the number of arbovirus infections is usually much higher. The initial clinical presentation can be highly confusing; therefore, laboratory confirmation is key to an accurate diagnosis. CASE PRESENTATION: A 19-year-old man presented to a peripheral health centre with an acute febrile illness. Dengue was initially suspected, but the patient deteriorated to a shock syndrome. Leptospirosis as well as a co-infection with Zika virus were both confirmed in the laboratory, the latter being clinically masked in this dual infection. CONCLUSION: This case highlights the importance of not only considering the differential diagnosis of acute febrile syndromes, but also to consider the possibility of dual infections in the context of global spread of arboviruses. The specific context of travellers returning from endemic areas and pregnant women is also highlighted and discussed.

Filariasis serosurvey, New Caledonia, South Pacific, 2013.

BACKGROUND: Lymphatic filariasis (LF) is a major public health problem in the Pacific. As the global prevalence of infection was not known in New Caledonia (NC), a serosurvey study was conducted by determining the prevalence of circulating filarial antigens, as recommended by the World Health Organization. FINDINGS: A cross sectional study on a 2 degree stratified sample was carried out from June to November 2013. Inclusion criteria were: individuals aged 2 to 80 y/o, who had been hospitalized or sought medical care for a non-infectious cause and who had been living in NC for more than 6 months. LF antigenic detection was performed using the immunocromatographic BinaxNOW filariasis card test (ICT). Among the 1,035 individuals tested, 7 were antigenic. The overall LF antigenic prevalence was 0.62% (CI 95% [0.60-0.63]). All patients were unrelated to each other; none of them presented clinical symptoms of LF. Four of the 7 ICT positive patients reported having travelled to LF endemic areas, 2 patients had never traveled outside NC and the last one had only traveled in non-endemic areas. For the 7 ICT positive patients, the research of microfilariae in blood smears and filarial DNA by PCR was negative. CONCLUSION: The prevalence of filarial antigenemia in NC is less than 1%, the threshold that defines the filarial endemic areas for WHO. Nevertheless, as two patients who had never travelled outside NC and one who had only travelled to non-endemic areas were antigenic, we cannot conclude that NC is totally free of LF.

Climate-based models for understanding and forecasting dengue epidemics.

BACKGROUND: Dengue dynamics are driven by complex interactions between human-hosts, mosquito-vectors and viruses that are influenced by environmental and climatic factors. The objectives of this study were to analyze and model the relationships between climate, Aedes aegypti vectors and dengue outbreaks in Noumea (New Caledonia), and to provide an early warning system. METHODOLOGY/PRINCIPAL FINDINGS: Epidemiological and meteorological data were analyzed from 1971 to 2010 in Noumea. Entomological surveillance indices were available from March 2000 to December 2009. During epidemic years, the distribution of dengue cases was highly seasonal. The epidemic peak (March-April) lagged the warmest temperature by 1-2 months and was in phase with maximum precipitations, relative humidity and entomological indices. Significant inter-annual correlations were observed between the risk of outbreak and summertime temperature, precipitations or relative humidity but not ENSO. Climate-based multivariate non-linear models were developed to estimate the yearly risk of dengue outbreak in Noumea. The best explicative meteorological variables were the number of days with maximal temperature exceeding 32°C during January-February-March and the number of days with maximal relative humidity exceeding 95% during January. The best predictive variables were the maximal temperature in December and maximal relative humidity during October-November-December of the previous year. For a probability of dengue outbreak above 65% in leave-one-out cross validation, the explicative model predicted 94% of the epidemic years and 79% of the non epidemic years, and the predictive model 79% and 65%, respectively. CONCLUSIONS/SIGNIFICANCE: The epidemic dynamics of dengue in Noumea were essentially driven by climate during the last forty years. Specific conditions based on maximal temperature and relative humidity thresholds were determinant in outbreaks occurrence. Their persistence was also crucial. An operational model that will enable health authorities to anticipate the outbreak risk was successfully developed. Similar models may be developed to improve dengue management in other countries.

Influenza A(H1N1)2009 in the French Pacific territories: assessment of the epidemic wave during the austral winter.

The three French territories in the Pacific (New Caledonia [NC], French Polynesia [FP] and Wallis and Futuna [WF]) have been affected by an outbreak of influenza A(H1N1)2009 during the austral winter of 2009. This wave of influenza-like illness was characterized by a short duration (approximately 8 weeks) and high attack rates: 16-18% in NC and FP, 28% in Wallis and 38% in Futuna. The number of infected patients requiring hospitalization in critical care services and the number of deaths were, respectively, 21 and 10 in NC and 13 and 7 in FP (none in WF). Diabetes, cardiac and pulmonary diseases, obesity in adults, neuromuscular diseases in children, and Oceanic origin were frequently observed among severe cases and deaths. A significant proportion of the population remains susceptible to A(H1N1)2009, making the occurrence of a second wave likely. A state of preparedness and control efforts must be implemented, based on preventive measures (immunization), as well as combined clinical and virological surveillance and health organization.