Risk of sexual transmission of Zika virus infection: a study among sex workers and their clients in an endemic area of coastal Ecuador

Lead Research Organisation: St George's University of London
Department Name: Institute of Infection & Immunity


Zika Virus (ZIKV) is a flavivirus transmitted to humans through the bite of Aedes mosquitoes, recently
epidemic in the Americas in 2015. There is currently no vaccine or treatment for ZIKV. ZIKV is
asymptomatic in approximately 80% of those infected, with symptomatic cases displaying mild febrile
illness. However, during the ongoing Latin America epidemic, concurrent reporting of severe
neurologic complications and adverse foetal outcomes in infected pregnant women became cause for
concern. ZIKV is now considered causally linked to microcephaly in new-borns with unknown cofactors
perhaps accounting for regional variation in incidence in Latin America.
In addition to classic transmission, it has become apparent that ZIKV follows in the footsteps of Ebola.
Virus is persistent in semen and vulvovaginal fluids post-infection, with increasing numbers of case
reports of sexual transmission between humans in the absence of classical mosquito transmission
pathways. If sexual transmission proves to be an established transmission route, mosquito control
efforts alone may not be enough to curb the transition of ZIKV from sporadic epidemic to sustained
endemicity in regions with capable vectors.
The project will initially determine the baseline seroprevalence of ZIKV in the District of Quininde,
Esmeraldas Province, Ecuador among high-risk groups for STIs. Female sex workers will be recruited
and serologically screened for ZIKV, and other mosquito borne viruses endemic to the region. Samples
from sex worker populations will be compared to those of an age and gender-matched control group of
women of childbearing age attending antenatal clinics at the public hospital in Quininde, to determine if
there is a higher prevalence of ZIKV in those with 'high' risk sexual behaviours to estimate the possible
contribution of sexual transmission to overall ZIKV burden. Participants will also be administered a
questionnaire collecting information on relevant demographic, socioeconomic and lifestyle information
(including sensitive sexual and other high risk behaviours such as consistency of condom use, extragenital
sex and illicit drug use).
This PhD project addresses aspects of all four Strategic Aims laid out by the Medical Research Council
(MRC, Research Changes Lives, MRC Strategic Plan 2014-2019
Strategic Aim 1: Research that Delivers; Theme Two "Living a Long and Healthy Life" AND
Strategic Aim 2: Research to the people
Assessment of risk factors for sexual transmission, subsequently informing targeted
education/screening of high-risk groups, as well as enhancing public health awareness efforts
surrounding ZIKV.
Strategic Aim 3: Going Global
By working within partner laboratories in Ecuador, our project not only fosters collaboration
between St George's University London, the MRC LID programme and the International
University (of Ecuador), but also builds capacity within Ecuador.
The findings of this project have the potential to support advocacy for female and sex worker
sexual health and rights in a country, where birth control and condoms are not widely available
or used.
Strategic Aim 4: Supporting Scientists, Capacity and Skills
The student will undergo training in the following areas;
Quantitative Skills
Epidemiological questionnaire creation and analysis
Molecular, genomic and phylogenetic techniques
Interdisciplinary Skills
Collaboration with social and qualitative scientists to develop questionnaires and
ethically/socially robust project protocols
Working with laboratory scientists to develop molecular and 'omic skills
Working with local settings in Ecuador to develop field epidemiology and Spanish language
Whole Organism Physiology
Developing an understanding of ZIKV infection kinetics within patients
ZIKV genomic analysis to understand symptomatic and biological presentation of ZIKV


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