Eric D'Ortenzio

Chikungunya Virus and the Mosquito Vector Aedes aegypti in New Caledonia (South Pacific Region)

Chikungunya virus (CHIKV) is transmitted to humans through the bite of Aedes mosquitoes. During the 2005-2006 epidemic that occurred in the Indian Ocean Islands, a viral strain harboring a substitution of an alanine to valine at position 226 (E1-A226V) of the E1 glycoprotein enhanced the transmissibility of CHIKV by Aedes albopictus. In March 2011, autochthonous transmission of CHIKV was reported in New Caledonia (NC), an island located in the southwest Pacific Ocean. This was the first report of local chikungunya (CHIK) transmission in this region of the world. Phylogenetic analysis based on the complete genome demonstrated that the CHIKV-NC strain isolated from the first autochthonous human case belongs to the Asian lineage. This is consistent with the Indonesian origin of CHIK cases previously imported and detected. Thus the CHIKV-NC does not present a valine substitution at position E1-226. In New Caledonia, the putative vector of CHIKV is Aedes aegypti, since no other potential vector has ever been described. For example, A. albopictus is not found in NC. Vector competence experiments showed that A. aegypti from New Caledonia was able to transmit, as early as 3 days post-infection, two CHIKV strains: CHIKV-NC belonging to the Asian lineage, and CHIKV-RE from Reunion Island harboring the E1-A226V mutation. Thus the extrinsic incubation period of both CHIKV strains in this vector species could be considered to be quite short. These results illustrate the threat of the spread of CHIKV in the South Pacific region. From February to June 2011 (the end of the alert), only 33 cases were detected. Implementation of drastic vector control measures and the occurrence of the cold season probably helped to limit the extent of the outbreak, but other factors may have also been involved and are discussed.

A review of the dynamics and severity of the pandemic A(H1N1) influenza virus on Réunion Island, 2009

On Reunion Island, in response to the threat of emergence of the pandemic influenza A(H1N1)2009 virus, we implemented enhanced influenza surveillance from May 2009 onwards in order to detect the introduction of pandemic H1N1 influenza and to monitor its spread and impact on public health. The first 2009 pandemic influenza A(H1N1) virus was identified in Réunion on July 5, 2009, in a traveller returning from Australia; seasonal influenza B virus activity had already been detected. By the end of July, a sustained community pandemic virus transmission had been established. Pandemic H1N1 influenza activity peaked during week 35 (24-30 August 2009), 4 weeks after the beginning of the epidemic. The epidemic ended on week 38 and had lasted 9 weeks. During these 9 weeks, an estimated 66 915 persons who consulted a physician could have been infected by the influenza A(H1N1)2009 virus, giving a cumulative attack rate for consultants of 8.26%. Taking into account the people who did not consult, the total number of infected persons reached 104 067, giving a cumulative attack rate for symptomatics of 12.85%. The crude fatality rate (CFR) for influenza A(H1N1)2009 and the CFR for acute respiratory infection was 0.7/10 000 cases. Our data show that influenza pandemic did not have a health impact on overall mortality on Réunion Island. These findings demonstrate the value of an integrated epidemiological, virological and hospital surveillance programme to monitor the scope of an epidemic, identify circulating strains and provide some guidance to public health control measures.

Prevention of HIV spread during the Ebola outbreak in Guinea

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Seroepidemiology of Dengue Virus in Mayotte, Indian Ocean, 2006

Background Although Dengue virus (DENV) circulation had been documented in neighbouring South-western Indian Ocean Islands, its presence in Mayotte is poorly characterised. To address this issue, we aimed to assess the seroprevalence of dengue IgG antibodies (DENV-IgG Ab) among the population and to investigate potential associations with individual and household characteristics. Methods/Principal Findings In November–December 2006 we conducted a cross-sectional serologic survey in Mayotte among 1,154 inhabitants aged ≥2 years by using a multistage cluster random sampling method. The overall prevalence of DENV-specific IgG antibodies (ELISA) was 22.73% (95% CI, 18.16–27.31). The age-specific seroprevalence increased with age (χ2 for trend = 11.86, P<0.0006), and was linked with previous known outbreaks in this region. In multivariate analysis, older age, being born in the Comoros and living in a household with a low socioeconomic index were positively associated with DENV IgG antibody positivity. Conclusions These findings document substantial prior exposure of the population of Mayotte to DENV and highlight the risk of severe illness due to the possibility of sequential DENV infections. Further investigations characterizing current DENV circulation patterns and associated serotypes are needed.

Pandemic influenza 2009 on Réunion Island: A mild wave linked to a low reproduction number.

We studied the epidemic trend following the introduction of the pandemic A(H1N1) 2009 in the subtropical Réunion Island. There, the pandemic wave started from week 30 and lasted until week 38, with an estimated attack rate of 12.85 % for symptomatic infections. The best estimate for the initial reproduction number was Ri = 1.26 [1.08; 1.49]. It results that the herd immunity necessary to stop the epidemic growth is of the same magnitude than the attack rate. Thus, a second wave before the 2010 austral winter seems unlikely, unless a viral mutation.

Febrile illness at the emergency department of Cayenne Hospital, French Guiana

Febrile illness is a common cause of attendance at emergency departments. The purpose of this study was to describe infectious aetiologies of fever in a tropical setting. We prospectively included 1443 febrile patients, all French Guiana residents, who presented at Cayenne Hospital emergency department. This report will propose an overview of aetiologies of febrile illness in French Guiana, and tropical diseases such as malaria and arbovirus infections are discussed. Almost 30% of fevers remained unexplained. Further prospective multicentre studies are warranted to improve the diagnosis of overlooked pathogens in French Guiana. Such studies would lead to conclusions of specific interest in the travel medicine field.

Jarisch–Herxheimer Reaction Among Patients with Leptospirosis: Incidence and Risk Factors

AbstractA Jarisch-Herxheimer reaction (JHR) may be precipitated after initiation of chemotherapy in spirochetal diseases, including leptospirosis. However, a clear idea of the importance of JHR in this disease is lacking. The incidence of and risk factors for JHR were investigated retrospectively among 262 patients with confirmed leptospirosis who received amoxicillin treatment in New Caledonia and Futuna. The overall rate of JHR was 21% (12% in New Caledonia and 44% in Futuna). Two risk factors were independently associated with JHR occurrence: Leptospira interrogans serogroup Australis as the infecting strain (odds ratio [OR] = 2.60, confidence interval [CI] = 1.40-5.62) and delays < 3 days between the onset of symptoms and the initiation of antibiotherapy (OR = 2.14, CI = 1.11-4.38). Clinicians should be aware of JHR as a potential complication of leptospirosis. Strain-related factors associated with JHR occurrence and its impact on outcome remains to be explored.

Dengue outbreaks: a constant risk for Reunion Island. Results from a seroprevalence study among blood donors.

BACKGROUND Immunity against dengue virus (DENV) on Reunion Island could play an important role in the risk of dengue outbreaks but is rather unknown. A study was performed to estimate seroprevalence of antibodies against DENV among blood donors. METHODS An age- and sex-stratified sample of 1825 sera was randomly selected. RESULTS Overall seroprevalence was 3.1% (95% CI: 2.2-3.9%); seroprevalence increased with age and was much higher in women than in men. CONCLUSION The low level of herd immunity is consistent with the absence of an endemic circulation of DENV, and makes it probable that Reunion Island will face future outbreaks.

Teaching anthropology to medical students

As a longtime enthusiast of The Lancet, I have been irritated many times by the often-meaningless quotes on the front cover of the journal. I consider these a waste of precious space. The quote on the Nov 1 issue referring to the Culture and Health Commission by David Napier and colleagues, was especially unacceptable: “The systematic neglect of culture in health and health care is the single biggest barrier to the advancement of the highest standard of health worldwide”. I wonder who can probably choose such an absurd and cynical statement. From my experience as a physician who has worked in many developing countries, it is the lack or unequal distribution of resources, rather than neglect of culture, that prevents progress in achievement of higher health-care standards. I highly recommend that The Lancet return to its old design, with content information on the front cover page to be seen at first glance. That way, the journal would save nearly one page for real medical information, and avoid printing meaningless nonsense.

Scientific journalism in Africa to help fight global health emergencies

The epidemic of the Ebola virus disease is not over yet because of persisting fear, mistrust, and opposition in Guinea, Liberia, and Sierra Leone. In view of the absence of an effective vaccine or treatment for this disease hitherto, outbreak control relies on isolation measures, monitoring contact cases, and disseminating preventive advice. However, despite the crucial importance of communication in outbreak contexts, there is no clear proposal from international agencies to improve the quality of broadcasted information in the wake of this epidemic. Media, such as radio and newspapers, can have a huge eff ect on individual and community opinion during outbreaks of communicable diseases—eg, exaggeration or reassurance from the media might exacerbate or temper people’s perceived risk of the Ebola virus disease. Along with sustaining and strengthening depleted health-care systems, enhanced communication through inexpensive methods is most needed, such as the media quickly delivering vital information to aff ected or at risk communities. However, journalists are not necessarily trained to provide adequate information about outbreaks. In 2015, in a review of Ebola-related articles published in epidemic countries, we noted that crucial intervention aspects (eg, contact cases lost to follow-up) were not mentioned, whereas a contextual analysis of opposing events (eg, dissimulation of dead bodies, non-compliance, or uncooperative contacts) was rarely completed. Almost none of the articles identifying opposing situations mentioned clear, comprehensive, accessible, and constructive public health messages. Similar results have been reported in the very few systematic reviews of newspapers done in aff ected and neighbouring African countries, including Guinea and Cameroon. Increasing journalists’ scientific knowledge could help them to broadcast the correct information about an associated risk of infection with potential epidemics and also could ease implementation of efficient public health measures. Journalists from high-income countries could share their knowledge and experience with their African counterparts during public health crises to help raise a community’s awareness. Some institutions are accustomed to participating in such capacity-building programmes (eg, Solthis) through existing media partnership cooperation networks. Dedicated financial support and policy initiatives are needed to create opportunities to raise awarness among journalists, both in epidemiology and medical anthropology, through workshops on epidemics. Mobilisation of journalists and their media would have indisputable benefi ts, including creating a critical group of journalists aware of pubic health and social sciences, and fortifying collaboration between the media and other health actors in outbreak contexts.