Surveillance of dengue: evolution of surveillance strategies during a large outbreak, Réunion, France

Issue

After a period of low-level circulation of a few cases per week during 2017, La Réunion experienced an outbreak of dengue in 2018 followed by a second and ongoing larger epidemic wave in 2019. Various surveillance systems have been progressively implemented to monitor and characterize the outbreak.

Methods

All laboratory diagnoses of dengue are routinely notified to the regional health authority (RHA) for investigation. With the outbreak onset additional programmes were implemented including the monitoring of presentations to emergency departments (EDs) and hospitalisations of dengue cases. In addition, all death notifications to the RHA which cite dengue are reviewed by an expert committee and the cause of death classified as directly, indirectly or unrelated to dengue. Finally, weekly data from a sentinel network of general practitioners is used to estimate the number of community consultations with dengue-like illness across the island.

Results

In 2017, 97 dengue cases were notified, with low level circulation continuing through the austral winter. In 2018, 6,679 cases (exclusively serotype 2) were notified. Western and southern regions of the island were most affected. The supplementary surveillance identified over 500 ED presentations for dengue-like illness and 160 hospitalisations. Three deaths were determined to be directly due to dengue, while 3 were indirectly related. Finally, there was an estimated 26,000 consultations for dengue-like illness in the community. After a second winter of persistent circulation, a second epidemic wave commenced in December 2018, and is still ongoing.

Lessons

The implementation of additional surveillance systems enabled a better understanding of the magnitude and impact of the outbreak. The use of sentinel network allowed the estimation of the number of people affected in the community without a laboratory diagnosis. The ongoing viral circulation since 2017 suggests a high risk of endemisation of dengue on the island.

Key messages

The outbreak has had a significant impact of health and community health services, and on the wider population. The second consecutive austral winter with interrupted transmission suggest a high risk of endemisation.

Sentinel physician's network in Reunion Island: a tool for infectious diseases surveillance

The surveillance of infectious diseases in Reunion Island is based on a sentinel network of family physicians (FPs) coordinated by the Indian Ocean regional institute for public health surveillance (French acronym OI Cire). The objectives are to identify and monitor outbreaks of influenza, gastroenteritis, and chicken pox, and to characterize circulating influenza viruses. The network can monitor other potentially epidemic diseases.

METHOD

The Réunion sentinel network ensures a continuous and permanent surveillance. Physicians send their weekly activity data to the Cire that collects, processes, and interprets it; they also collect samples for biological surveillance of influenza. Statistical thresholds, based on historical data and the estimated numbers of incident cases, are calculated to follow the trend, detect outbreaks, and quantify their impact.

RESULTS

The network currently includes 56 FPs and pediatricians, accounting for 6.5% of FPs on the island. The network has clarified the seasonality of influenza during the austral winter and identified the seasonality of acute diarrhea with an epidemic peak when school starts in August. The sentinel FPs's reports allowed monitoring the epidemic trend and estimating the number of cases during the 2005 and 2006 chikungunya outbreaks and 2009 influenza A (H1N1) outbreaks.

CONCLUSION

The network has proven its contribution, responsiveness, and reliability for epidemiological surveillance during outbreak. It is an essential tool for infectious diseases surveillance in Reunion Island.

Influenza season in Réunion dominated by influenza B virus circulation associated with numerous cases of severe disease, France, 2014

The 2014 seasonal influenza in Réunion, a French overseas territory in the southern hemisphere, was dominated by influenza B. Resulting morbidity impacted public health. Relative to the total number of all-cause consultations over the whole season, the rate of acute respiratory infection (ARI) consultations was 6.5%. Severe disease occurred in 32 laboratory-confirmed influenza cases (31.7 per 100,000 ARI consultations), 16 with influenza B. The observed disease dynamics could present a potential scenario for the next European influenza season.

Réunion, a sentinel territory for influenza surveillance in Europe

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[Severe forms of chikungunya virus infection in a pediatric intensive care unit on Reunion Island]

In 2005-2006, an unexpected, massive outbreak of chikungunya occurred on Reunion Island, a French overseas territory in the Indian Ocean. This arboviral infection transmitted by a mosquito of the Aedes genus is usually benign. A surprising feature of the Reunion Island epidemic was the occurrence of rare severe forms involving adults as well as children.

OBJECTIVES

The purpose of this report is to describe severe forms of chikungunya observed in children hospitalized in a pediatric intensive care unit.

PATIENTS AND METHODS

This retrospective single-center study was conducted from January 1st to April 30th, 2006. Children between 1 month and 15 years admitted to the pediatric intensive care unit with proven chikungunya infection were included.

RESULTS

A total of 9 children were included. The main manifestations were extensive skin blisters in 5 cases, neurological symptoms (encephalopathy) in 4, cardiac complications (myocarditis, hemodynamic disorders) in 5 and bleeding in 1. Two children died. The causes of death were circulatory failure associated with coma and massive hemorrhage in one case and post-infectious encephalitis in the other. Three survivors present long-term neurologic or dermatologic sequels.

DISCUSSION

Severe cases of chikungunya in children provide a stark reminder of the cardiac and neurological tropism of the virus and its hemorrhagic forms with high potential mortality and morbidity. These cases underline the need for personal protection measures and for research to develop specific antiviral therapy and vaccines to prevent potentially lethal forms of the disease.

[Physiopathology of chronic arthritis following chikungunya infection in man]

Chronic arthritis following chikungunya infection has no specific treatment. Studies on mice have confirmed involvement of fibroblasts and myoblasts as target cells replicating the virus and shown that macrophages play a key role in the innate immune response involving multiple cytokines and chimiokines. Paradoxically, TH1 and TH2 cytokine levels do not increase significantly during the acute and chronic phases, with the exception of interferon-gamma and IL12 that rise dramatically during the acute phase. The level of IL12 returns to normal in patients who recover. In contrast, patients who develop chronic arthritis show persistently high IL12 levels along with IFN-alpha within PBMC. Histologic examination of synovia reveals joint inflammation due to macrophages containing viral material. Metallo-protease (MMP2) also contributes to tissue damage. Chikungunya virus leads to apoptosis by both the intrinsic and extrinsic pathways.

[Disseminated histoplasmosis caused by Histoplasma capsulatum in a renal transplant patient: first case report in the Reunion Island]

The purpose of this report is to describe the first case of indigenous disseminated histoplasmosis caused by Histoplasma capsulatum in a patient on immunosuppression 22 months after renal transplantation in the Reunion Island. Involvement was predominantly pulmonary and outcome was rapidly fatal. Diagnosis based on isolation of characteristic intramacrophagic Histoplasma capsulatum yeast cells from bronchoalveolar fluid was delayed since indigenous cases of this opportunistic infection were unprecedented. In addition to demonstrating the difficulty of achieving diagnosis in places located outside endemic areas without modern facilities, this case underlines the potentially the poor prognosis of disseminated histoplasmosis. This disease should be included in differential diagnosis in the Reunion Island where many patients undergo immunosuppresion and receive organs shipped in from outside locations.

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

First infections with the 2009 pandemic H1N1 influenza virus were identified on Réunion 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 Réunion 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.

Sporadic cases of chikungunya, Réunion Island, August 2009

On 28 August 2009, French authorities reported five cases of chikungunya fever on Réunion 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.

[Primary amebic meningoencephalitis: 1st case observed in Madagascar]

The primary amebic meningoencephalitis is an acute suppurative infection that involves both the brain and the meninges. It is caused by Naegleria fowleri and is a very rare and fulminating condition, so far nearly always fatal. We report the first case in the area of Southern part of Indian Ocean that occured in a 7-year old French boy living in Madagascar. It is assumed that the disease was contracted by swimming in warm fresh water in a lake of the Madagascar east coast. Clinical signs began 10-12 days after exposure, associating headache, vomiting and pyrexia (39-40 degrees C). Upon admission in a Madagascar hospital, the patient was started on antibiotics, that did not control the disease and soon presented with a loss of consciousness and a delirium. He was transferred to Reunion island (Centre Hospitalier Départemental Félix-Guyon), where the diagnosis of primary amebic meningoencephalitis was confirmed. Therefore, he was started on high-dose of intraspinal amphotericin B, IV amphotericin B lipid complex and tetracycline. He developed myocarditis, diabetes insipidus, deep coma and subsequently died a week later. The diagnosis of amebic meningoencephalitis was based on: -- the cerebrospinal fluid examination that confirmed the diagnosis of purulent meningitis: 420 leucocytes (76% polynuclears, 14% lymphocytes), 90 red blood cells, and showed 50 ameboid trophozoites per 100 leucocytes, approximately 20 microm in size. -- the flagellate transformation test in distilled water showed two anterior flagellas that confirmed the genus Naegleria.

[Severe forms of eosinophilic meningitis in infants of Mayotte. Apropos of 3 cases]

BACKGROUND

Eosinophilic meningitis caused by Angiostrongylus cantonensis is widespread in Southeast Asia and the Pacific islands. Adults develop transient meningitis with a benign course, whilst severe or fatal disease may occur in pediatric patients.

CASE REPORTS

Three infant girls, aged 8 to 11 months, living on the island of Mayotte, developed fever, hypotonia, coma (2 cases), and, for one of them, seizures. Eosinophilia was detected in the peripheral blood and cerebrospinal fluid. Secondary, flaccid quadraplegia (1 case) or paraplegia (2 cases) with absence of deep tendon reflexes, urinary retention and anal incontinence were noted. Three patients had autonomic dysfunction. Computerized tomography showed enlarged ventricles and cerebral subarachnoid spaces. One patient had sequelae. Two patients could not be followed. Retrospectively, the diagnosis of angiostrongylus infection was established for two infants by a serological study.

CONCLUSION

We report three new cases of infants with severe Angiostrongylus cantonensis infection in the French island of Mayotte (Comoro Islands). In this Indian Ocean area, eosinophilic meningitis seems to occur exclusively in infants and with severe radiculomyeloencephalitic forms.

[Angiostrongylosis in infants in Reunion and Mayotte. Apropos of 3 cases of eosinophilic meningitis including 1 fatal radiculo-myeloencephalitis with hydrocephalus]

BACKGROUND

Eosinophilic meningitis caused by Angiostrongylus cantonensis is widespread in Southeast Asia and Pacific islands. Adults develop a transient meningitis with a benign course but severe or fatal disease may occur in pediatric patients.

CASE REPORT

Case 1. A 11-month-old boy living in Mayotte island was hospitalized a few days with fever and skin rash following by seizure, coma, flaccid quadraplegia, absence of deep tendon reflexes, urinary retention and anal incontinence. Eosinophilia was observed in peripheral blood and cerebrospinal fluid. He further developed a triventricular hydrocephalus treated by ventriculoperitoneal shunt. The child died 3 weeks later. A serodiagnosis of angiostrongylus infestation was restrospectively established. Case reports 2 and 3.-Two infants, 10 and 11-month-old-boys, living in Reunion island, developed fever and vomitings, irritability and, for one of them, unilateral sixth cranial nerve palsy. There was eosinophilia in the peripheral blood and in the cerebrospinal fluid. All symptoms progressively disappeared with complete recovery. The suspected diagnosis of angiostrongylus infestation was confirmed by the serology.

CONCLUSION

We report the first case of Angiostrongylus cantonensis infection in the French island of Mayone (Comoro Islands) and we confirm the presence of this disease in Reunion island. In this Indian Ocean area, eosinophilic meningitis occurs most of the time in infants with sometimes severe radiculomyeloencephalitic forms.

Production of elastase, exotoxin A, and alkaline protease in sputa during pulmonary exacerbation of cystic fibrosis in patients chronically infected by Pseudomonas aeruginosa

Secretion of Pseudomonas aeruginosa elastase, exotoxin A, and alkaline protease in sputum during bronchopulmonary exacerbations was examined in 18 cystic fibrosis patients chronically infected with this microorganism. The patients were studied during one or several exacerbation periods necessitating hospitalizations of 12 to 20 days. In all cases, P. aeruginosa was present in bronchial secretions at admission and was not eradicated after treatment. The P. aeruginosa density decreased significantly after antibiotic therapy but remained greater than 10(6) CFU/g of sputum in most cases. Significant amounts of P. aeruginosa exoproteins were measured in total homogenized bronchial secretions by immunoenzymatic assays. The detection of higher levels of exoproteins at admission, the significant decrease after treatment, and the absence of exoproteins during intercrisis phases constituted arguments for a renewal of virulence of P. aeruginosa during exacerbations. Nevertheless, the concomitant changes in bacteria load and the triggering of the inflammatory process and immune complex formation could also contribute to pulmonary exacerbations.

Immunoenzymometric assays for alkaline protease and exotoxin A from Pseudomonas aeruginosa: development and use in detecting exoproteins in clinical isolates from patients with cystic fibrosis

Using immunoenzymometric assays, the production of elastase, alkaline protease and exotoxin A was determined in culture supernatants of 35 strains of Pseudomonas aeruginosa isolated from patients suffering from cystic fibrosis. The assays were simple, specific, sensitive and reproducible, and permitted the determination of low levels of exoproteins. A large strain variability of exoprotein production was found. Most of the strains secreted all three exoproteins, but six out of the 35 strains (17%) did not secrete at least one of the three (< 0.3 microgram/l). A significant correlation was observed between elastase and exotoxin A productions (r = 0.697, p < 0.001).

[Production of elastase, exotoxin A and alkaline protease during bronchopulmonary exacerbations in patients with mucoviscidosis chronically infected by Pseudomonas aeruginosa]

The authors have studied the production of exoproteins by Pseudomonas aeruginosa in the sputa of 18 patients suffering from cystic fibrosis, during 29 bronchopulmonary exacerbations and also after the recovery of a stable state. Significant levels of exoproteins were detected but with a large heterogenity of intra and inter individual variations. A significant decrease in the production of the three exoproteins was found after twelve days of antibiotherapy, without any correlation between exoprotein levels and colony forming units in the sputa. During the intercrisis phase, exoproteins levels were practically undetectable. These facts and the good correlation between clinical symptoms support the hypothesis of a renewal of virulence of Pseudomonas aeruginosa during these periods of bronchopulmonary exacerbation in cystic fibrosis.

Direct double antibody sandwich immunoassay for Pseudomonas aeruginosa elastase

A direct sandwich enzyme immunoassay was developed in order to quantify Pseudomonas aeruginosa elastase. As a solid phase the wells of a microtitre plate were coated with specific IgG and horseradish peroxidase labelled IgG was used as the second antibody. The detection limit of the assay was 0.26 ng/ml and a good agreement was found with elastolytic activity determined using elastin-Congo red. This assay was simple, specific, sensitive and reproducible, and permits the determination of low levels of elastase.