Date of Award

Summer 8-10-2021

Degree Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

Public Health

First Advisor

Christine Stauber

Second Advisor

Lisa Casanova

Abstract

INTRODUCTION: Zika virus (ZIKV), an enveloped virus of the species Flavivirus, was historically, rarely associated with human infection and diseases, but that changed with large outbreaks in French Polynesia in 2013 and then Brazil in 2015. With approximately 80% of ZIKV infections being asymptomatic and a lack of adequate surveillance methods and healthcare access and resources, Brazil had challenges in determining the true burden of infection in affected communities. Though the COVID-19 pandemic has increased the evidence of the detectability of enveloped viruses in wastewater, but there are still research gaps regarding how environmental conditions may affect detection of enveloped viruses such as ZIKV.

AIM: The objectives of this study are to utilize wastewater-based epidemiological methods as a means to detect and evaluate the stability of ZIKV RNA in primary influent and surface water under different environmental conditions including temperature, water matrices, and inoculation concentrations.

METHODS: ZIKV MEX 1-44 was added to primary influent from a local municipal wastewater treatment plant and surface water from a local stream in Atlanta, Ga. Three experiments were conducted. to assess the detection and persistence of ZIKV RNA in different conditions including different inoculation concentrations, water conditions and temperature. RNA was extracted at days 0, 1, 3, 7, 14, 21, and 28 for all experiments. Digital droplet polymerase chain reaction (ddPCR) was used to quantify ZIKV RNA concentration. Log10 concentrations and Log10 reductions (Ct/C0) were calculated and graphed to compare ZIKV RNA decay over time under the different conditions.

RESULTS: ZIKV RNA was detected in all samples at all times, temperatures, and water matrices with ddPCR during the month-long experiment. Across experiments, ZIKV RNA degradation increased in surface water, at increasing temperatures, and at lower inoculation concentrations. The ZIKV RNA signal decayed most rapidly in surface water at 35°C, with little to no decrease observed at 4°C across water matrices.

DISCUSSION: ZIKV RNA is more environmentally stable than previously assumed. This study increased the body of evidence for the methods of detection and the stability of enveloped viruses, such as ZIKV, in various waters, portraying how environmental conditions may affect said stability. Cost-effective and wide-scale population level surveillance methods to detect ZIKV RNA in wastewater and environmental waters such as these, are of increasing importance to better understand the burden of ZIKV in a community and to monitor for not only ZIKV, but also other emerging and reemerging pathogens. Such methods have the potential to be utilized in low-resources settings, filling the gaps, and overcoming the challenges of clinical surveillance.

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