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Publications (63)
Transmission trees can be established through detailed contact histories, statistical or phylogenetic inference, or a combination of methods. Each approach has its limitations, and the extent to which they succeed in revealing a ‘true’ transmission history remains unclear. In this study, we compared the transmission trees obtained through contact t...
Typhoid is an endemic in Fiji with increases observed since the early 2000s and frequent outbreaks reported. We assessed the diagnostic accuracy of currently available typhoid rapid diagnostic tests (RDTs) (TUBEX, Typhidot Rapid, and Test-It assay) to establish their performance against blood culture in Fiji and to examine their suitability for rap...
Background: ODK provides software and standards that are popular solutions for off-grid electronic data collection and has substantial code overlap and interoperability with a number of related software products including CommCare, Enketo, Ona, SurveyCTO, and KoBoToolbox. These tools provide open-source options for off-grid use in public health dat...
Zika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIK...
Background
ODK provides software and standards that are popular solutions for off-grid electronic data collection and has substantial code overlap and interoperability with a number of related software products including CommCare, Enketo, Ona, SurveyCTO and KoBoToolbox. In combination with the use of statistical analysis software such as R, these t...
Background
ODK provides software and standards that are popular solutions for off-grid electronic data collection and are the basis of related products like CommCare, Enketo, Ona, SurveyCTO and KoBoToolbox. In combination with the use of statistical analysis software such as R, these tools provide fully open-source options for off-grid use in publi...
It has been commonly assumed that Zika virus (ZIKV) infection confers long-term protection against reinfection, preventing ZIKV from re-emerging in previously affected areas for several years. However, the long-term immune response to ZIKV following an outbreak remains poorly documented. We compared results from eight serological surveys before and...
Objectives:
In Fiji, autochthonous chikungunya virus (CHIKV) infection was first detected in March 2015. In a previous serosurvey conducted during October-November 2015, we reported a prevalence of anti-CHIKV IgG antibodies of 0.9%. In the present study, we investigated the seroprevalence of CHIKV two years after its emergence in Fiji.
Methods:...
Zika and chikungunya viruses were first detected in Fiji in 2015. Examining surveillance and phylogenetic and serologic data, we found evidence of low-level transmission of Zika and chikungunya viruses during 2013-2017, in contrast to the major outbreaks caused by closely related virus strains in other Pacific Island countries.
Public health emergencies, such as an Ebola disease outbreak, provide a complex and challenging environment for the evaluation of candidate vaccines. Here, we outline the need for flexible and responsive vaccine trial designs to be used in public health emergencies, and we summarize recommendations for their use in this setting.
Understanding risk factors for Ebola transmission is key for effective prediction and design of interventions. We used data on 860 cases in 129 chains of transmission from the latter half of the 2013-16 Ebola outbreak in Guinea. Using negative binomial regression, we determined characteristics associated with the number of secondary cases resulting...
A unique outbreak of Ross River virus (RRV) infection was reported in Fiji in 1979. In 2013, RRV seroprevalence among residents was 46.5% (362/778). Of the residents who were seronegative in 2013 and retested in 2015, 10.9% (21/192) had seroconverted to RRV, suggesting ongoing endemic circulation of RRV in Fiji.
A unique outbreak of Ross River virus (RRV) infection was reported in Fiji in 1979. In 2013, RRV seroprevalence among residents was 46.5% (362/778). Of the residents who were seronegative in 2013 and retested in 2015, 10.9% (21/192) had seroconverted to RRV, suggesting ongoing endemic circulation of RRV in Fiji.
Background
Serosurveys published following major outbreaks of Zika virus (ZIKV) have so far shown a high level of seroprevalence from samples collected within 12 months of the first confirmed case. A common assumption is that ZIKV infection confers long-term protection against reinfection, preventing ZIKV from re-emerging in previously affected are...
INTRODUCTION:Leptospirosis is a zoonotic disease responsible for over 1 million severe cases and 60,000 deaths annually. The wide range of animal hosts and complex environmental drivers of transmission make targeted interventions challenging, particularly when restricted to regression-based analyses which have limited ability to deal with complexit...
Dengue is a major health burden, but it can be challenging to examine transmission and evaluate control measures because outbreaks depend on multiple factors, including human population structure, prior immunity and climate. We combined population-representative paired sera collected before and after the 2013/14 dengue-3 outbreak in Fiji with surve...
Supplementary data and results tables.
Questionnaire that accompanied the 2015 serological survey in Central Division.
Serological, surveillance and climate data for the 2013/14 DENV-3 outbreak in Central Division.
Background:
Leptospirosis is a globally important zoonotic disease, with complex exposure pathways that depend on interactions between human beings, animals, and the environment. Major drivers of outbreaks include flooding, urbanisation, poverty, and agricultural intensification. The intensity of these drivers and their relative importance vary be...
Public Health Emergencies (PHEs) provide a complex and challenging environment for vaccine evaluation. Under the R&D Blueprint Plan of Action, the World Health Organization (WHO) has convened a group of experts to agree on standard procedures to rapidly evaluate experimental vaccines during PHEs while maintaining the highest scientific and ethical...
Leptospirosis is a globally important zoonotic disease, with complex exposure pathways that depend on interactions between humans, animals, and the environment. Major drivers of outbreaks include flooding, urbanisation, poverty, and agricultural intensification. The intensity of drivers and their relative importance vary between geographic areas an...
Risk maps of leptospirosis can be used to inform prevention and
control strategies, and provide eco‐epidemiological insights. Spatial Bayesian networks (SBNs) provide a novel approach for risk mapping and scenario modelling; advantages over more traditional methods include the visual and interactive interface; the ability to include spatial and non...
iFiji recently experienced a sharp increase in reported typhoid fever cases. To investigate geographic distribution and environmental risk factors associated with Salmonella enterica serovar Typhi infection, we conducted a cross-sectional cluster survey with associated serologic testing for Vi capsular antigen–specific antibodies (a marker for expo...
Additional information on role of environmental factors in shaping spatial distribution of Salmonella enterica serovar Typhi, Fiji.
Dengue is a major health burden, but it can be challenging to examine transmission dynamics and evaluate control measures because outbreaks depend on multiple factors, including human population structure, prior immunity and climate. We combined population-representative paired sera collected before and after the major 2013/14 dengue-3 outbreak in...
Empirical data on contact patterns can inform dynamic models of infectious disease transmission. Such information has not been widely reported from Pacific islands, nor strongly multi-ethnic settings, and few attempts have been made to quantify contact patterns relevant for the spread of gastrointestinal infections. As part of enteric fever investi...
Mealtime social contact questionnaire.
A questionnaire data collection tool with integrated interview guide for mealtime social contacts by meal, setting, age and ethnicity.
(DOCX)
Supplementary data excel file.
Sheet 1: line list of mealtime social contacts.
Sheet 2: line list of animal contacts.
Sheet 3: line list of travel in past week.
Sheet 4: line list of moving community.
(XLSX)
Seropositivity and social contact regression analysis.
(PDF)
Age distribution (count) of iTaukei and non-iTaukei in Fiji in A) 2007 census and B) 2013 social contact survey.
(TIF)
Animal contact by ethnicity and geography (A: owned livestock, B: other owned domesticated animals, C: physical contact with wild rodents).
(DOCX)
Lifetime prevalence of having moved community and moved in the last five years for A) all participants, B) iTaukei participants, C) non-iTaukei participants, by five-year age bands. Hollow points denote 95% confidence intervals.
(TIF)
Background:
In March, 2016, a flare-up of Ebola virus disease was reported in Guinea, and in response ring vaccination with the unlicensed rVSV-ZEBOV vaccine was introduced under expanded access, the first time that an Ebola vaccine has been used in an outbreak setting outside a clinical trial. Here we describe the safety of rVSV-ZEBOV candidate v...
Regression models are the standard approaches used in infectious disease epidemiology, but have limited ability to represent causality or complexity. We explore Bayesian networks (BNs) as an alternative approach for modelling infectious disease transmission, using leptospirosis as an example. Data were obtained from a leptospirosis study in Fiji in...
Fiji, an upper-middle income state in the Pacific Ocean, has experienced an increase in confirmed case notifications of enteric fever caused by Salmonella enterica serovar Typhi (S. Typhi). To characterize the epidemiology of typhoid exposure, we conducted a cross-sectional sero-epidemiological survey measuring IgG against the Vi antigen of S. Typh...
Serial anti-Vi IgG titres from convalescent confirmed typhoid cases.
(TIFF)
AIC by maximum likelihood for fixed effect model thresholds for anti-Vi IgG antibody waning to the threshold level in culture-confirmed typhoid cases.
(DOCX)
Supplementary information.
(PDF)
Design effects and ICC by 5-year age band, mainland Viti Levu and Vanua Levu.
(DOCX)
Seroprevalence for anti-Vi IgG at different ELISA unit thresholds amongst mainland residents (by self-reported vaccine status), Taveuni island residents and convalescent cases.
(DOCX)
Univariable risk factors for seropositivity with anti-Vi IgG on mainland Viti Levu & Vanua Levu at 64 ELISA unit threshold.
(DOCX)
Background:
By January, 2016, all known transmission chains of the Ebola virus disease (EVD) outbreak in west Africa had been stopped. However, there is concern about persistence of Ebola virus in the reproductive tract of men who have survived EVD. We aimed to use biostatistical modelling to describe the dynamics of Ebola virus RNA load in semina...
The population of Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid
fever, exhibits limited DNA sequence variation, which complicates efforts to rationally
discriminate individual isolates. Here we utilize data from whole-genome sequences (WGS)
of nearly 2,000 isolates sourced from over 60 countries to generate a robust g...
Background:
The WHO definition of trachomatous trichiasis (TT) is "at least one eyelash touching the globe, or evidence of recent epilation of in-turned eyelashes", reflecting the fact that epilation is used as a self-management tool for TT. In Fiji's Western Division, a high TT prevalence (8.7% in those aged ≥15 years) was reported in a 2012 surv...
Background:
Declining incidence and spatial heterogeneity complicated the design of phase 3 Ebola vaccine trials during the tail of the 2013-16 Ebola virus disease (EVD) epidemic in West Africa. Mathematical models can provide forecasts of expected incidence through time and can account for both vaccine efficacy in participants and effectiveness i...
Background:
rVSV-ZEBOV is a recombinant, replication competent vesicular stomatitis virus-based candidate vaccine expressing a surface glycoprotein of Zaire Ebolavirus. We tested the effect of rVSV-ZEBOV in preventing Ebola virus disease in contacts and contacts of contacts of recently confirmed cases in Guinea, west Africa.
Methods:
We did an o...
Objective To evaluate the effectiveness and cost of the pan-London pharmacy initiative, a programme that allows administration of seasonal influenza vaccination to eligible patients at pharmacies.
Design We analysed 2013–2015 data on vaccination uptake in pharmacies via the Sonar reporting system, and the total vaccination uptake via 2011–2015 ImmF...
Leptospirosis is an important zoonotic disease in the Pacific Islands. In Fiji, two successive cyclones and severe flooding in 2012 resulted in outbreaks with 576 reported cases and 7% case-fatality. We conducted a cross-sectional seroprevalence study and used an eco-epidemiological approach to characterize risk factors and drivers for human leptos...
Using an Ebola virus disease transmission model, we found that addition of ring vaccination at the outset of the West Africa epidemic might not have led to containment of this disease. However, in later stages of the epidemic or in outbreaks with less intense transmission or more effective control, this strategy could help eliminate the disease.
Ebola virus can persist in semen after recovery, potentially for months, which may impact the duration of enhanced surveillance required after interruption of transmission. We combined recent data on viral RNA persistence with weekly disease incidence to estimate the current number of semen-positive men in affected West African countries. We find t...
Objectives:
We investigate the chance of demonstrating Ebola vaccine efficacy in an individually randomised controlled trial implemented in the declining epidemic of Forécariah prefecture, Guinea.
Methods:
We extend a previously published dynamic transmission model to include a simulated individually randomised controlled trial of 100 000 partic...
A recombinant, replication-competent vesicular stomatitis virus-based vaccine expressing a surface glycoprotein of Zaire Ebolavirus (rVSV-ZEBOV) is a promising Ebola vaccine candidate. We report the results of an interim analysis of a trial of rVSV-ZEBOV in Guinea, west Africa.
For this open-label, cluster-randomised ring vaccination trial, suspect...
A World Health Organization expert meeting on Ebola vaccines proposed urgent safety and efficacy studies in response to the outbreak in West Africa. One approach to communicable disease control is ring vaccination of individuals at high risk of infection due to their social or geographical connection to a known case. This paper describes the protoc...
The emergence of multidrug-resistant (MDR) typhoid is a major global health threat affecting many countries where the disease is endemic. Here whole-genome sequence analysis of 1,832 Salmonella enterica serovar Typhi (S. Typhi) identifies a single dominant MDR lineage, H58, that has emerged and spread throughout Asia and Africa over the last 30 yea...
Despite a recommendation by the World Health Organization (WHO) that typhoid vaccines be considered for the control of endemic disease and outbreaks, programmatic use remains limited. Transmission models and economic evaluation may be informative in decision making about vaccine programme introductions and their role alongside other control measure...
Typhoid fever exists somewhere in the borderlines of the neglected tropical diseases. Its history in Europe and North America, and market for vaccination of travelers, means that typhoid is not entirely in the pharmaceutical public health wilderness. Travel immunization recommendations, however, are based on the results of efficacy trials performed...
The London 2012 Olympic and Paralympic Games will be one of the largest mass gathering events in British history. In order to minimise potential infectious disease threats related to the event, the Health Protection Agency (HPA) has set up a suite of robust and multisource surveillance systems. These include enhancements of already established syst...
