Cohort Study of Arbovirus and Other Emerging Virus Infections in Fiji: AEVI-Fiji Cohort.

Fiji National University910 enrolled

Overview

Background: Fiji, an archipelago in the South Pacific comprising 332 islands distributed among 4 health administrative divisions (Central, Western, Eastern, Northern), is particularly vulnerable to the (re-)emergence of arboviruses and respiratory viruses due to its sub-tropical climate, the presence of several mosquito vector species, and connections with many countries in the Pacific, Asia and North America. Over the past decades, the epidemiological landscape of arboviruses has shifted from the sequential circulation of each of the four dengue virus (DENV) serotypes to the emergence of Zika virus (ZIKV) and chikungunya virus (CHIKV), concomitantly to the concurrent circulation of multiple DENV serotypes. The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2020 significantly challenged Fiji's healthcare system, with the Delta variant alone accounting for approximately 700 deaths, while other respiratory viruses, such as influenza A and B, cause seasonal outbreaks. Despite these threats, comprehensive and up-to-date seroprevalence data remain scarce, limiting the capacity to inform and adapt public health policies. Methods: The cohort study of Arbovirus and other Emerging Virus Infections in Fiji (AEVI-Fiji cohort study) aims to estimate the prevalence of several arboviruses and respiratory viruses, track the evolution of individual immunity, and analyse transmission dynamics of these viruses within the Fijian population. This longitudinal study will span 38 months and will include about 900 willing participants aged six years and older, recruited from at least 210 households randomly selected across the Central Division. Four visits will be conducted 12 months apart in each household. During each visit, participants will complete a questionnaire capturing their demographic characteristics and history of infections with major arboviruses and respiratory viruses and will provide a blood sample for serological analysis. During the whole study period, participants with a suspected acute infection by an arbovirus or respiratory virus will be screened. Discussion: For the first time in Fiji, the AEVI-Fiji cohort study will generate longitudinal data to explore the determinants of both arbovirus and respiratory virus infections. The findings are expected to guide targeted public health strategies and enhance preparedness for future infectious disease threats in Fiji and the broader Oceania region.

Study Type

OBSERVATIONAL

Enrollment

910

Eligibility

Sex: ALLMin age: 6 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Individuals aged 6 years and older who reside in the Central Division of Fiji * Have lived in the selected household for at least six months at the time of enrollment Exclusion Criteria: * Pregnant women; * Women in labor, or breastfeeding mothers; * Individuals deprived of liberty by judicial or administrative decision; * Individuals under psychiatric care or admitted to a health or social care facility for purposes other than participation in the study; * Adults under legal protection or unable to provide informed consent; * Homeless individuals; * Individuals with severe disabilities preventing mobility; * Individuals unable to understand or complete the study questionnaire

Outcomes

Primary Outcomes

Level of herd immunity for arboviruses and respiratory viruses by conducting a seroprevalence survey among households including both children and adults In Central division of Fiji

Proportion of participants with Immunoglobulin type G (IgG) antibodies, detected in blood samples : IgG antibodies specific to a panel of arboviruses (including the four DENV serotypes, ZIKV, CHIKV, Ross River virus \[RRV\], yellow fever virus \[YFV\], Japanese encephalitis virus \[JEV\], West Nile virus \[WNV\]) and respiratory viruses (including influenza viruses A and B, SARS-CoV-2), as well as any major emerging pathogen (pathogen X) will be detected, using a multiplex microsphere immunoassay (MIA). Additionally, seroneutralisation tests will be performed to detect and quantify neutralising antibodies against the same panel of viruses. The IgG and neutralising antibody results for each virus will be combined to determine overall immune response (positive/negative) for the targeted viruses.

Time frame: From enrollment to the end of the first inclusion visit (V1) at month 12

Secondary Outcomes

Evolution of individual memory immunity for arboviruses and respiratory viruses by performing serological monitoring of the study participants over a period of 38 months

Proportion of participants with Immunoglobulin type G (IgG) antibodies, detected in blood samples : IgG antibodies specific to a panel of arboviruses (including each of the four DENV serotypes, ZIKV, CHIKV, RRV, YFV, JEV, WNV) and respiratory viruses (including influenza viruses A and B, SARS-CoV-2), as well as any major emerging pathogen (pathogen X) will be detected, using a MIA to track changes in antibody composition (seroconversion or seroreversion) and levels (increase, decrease, or stability), as well as possible cross-reaction phenomena. Additionally, seroneutralisation tests will be performed to detect and quantify neutralising antibodies against the same panel of viruses. The IgG and neutralising antibody results for each virus will be combined to determine overall immune response (positive/negative) for the targeted viruses.

Time frame: From enrollment to the end of the last visit (V4) at month 38

Systematic screening and sequencing of acute infections of the study participants over a period of 38 months

Systematic screening of acute infections for participants to a panel of arboviruses (including each of the four DENV serotypes, ZIKV, CHIKV, RRV, YFV, JEV, WNV) and respiratory viruses (including influenza viruses A and B, SARS-CoV-2), as well as any major emerging pathogen (pathogen X). Positive samples will undergo whole-genome sequencing. This screening and sequencing will allow identification of the viral strain responsible for each infection.