Tracking COVID-19 with wastewater to understand asymptomatic transmission

Abstract

Introduction: SARS-CoV-2 RNA is excreted in feces of most patients, therefore viral load in wastewater can be used as a surveillance tool to develop an early warning system to help and manage future pandemics.

Methods: We collected wastewater from 24 random locations at Bangkok city center and 26 nearby suburbs from July to December 2020. SARS-CoV-2 RNA copy numbers were measured using real-time polymerase chain reaction (PCR).

Results: SARS-CoV-2 RNA was detected in wastewater from both the city center and suburbs. Except for July, there were no significant differences in copy numbers between the city center and suburbs. Between October and November, a sharp rise in copy number was observed in both places followed by two to three times increase in December, related to SARS-CoV-2 cases reported for same month.

Conclusions: Our study provided the first dataset related to SARS-CoV-2 viral RNA in the wastewater of Bangkok. Our results suggest that wastewater could be used as a complementary source for detecting viral RNA and predicting upcoming outbreaks and waves.

Keywords: Asymptomatic transmission; COVID-19; SARS-CoV-2 in wastewater; SARS-CoV-2 viral RNA; Wastewater; Wastewater of Bangkok.

Figure 1

Viral loads of SARS-CoV-2 RNA copies in wastewater at each individual location of city center (n = 24) and suburbs (n = 26) from June to December. Each data point indicates the mean copy number of SARS-CoV-2 RNA of each individual location per month. The lower and upper boundaries of the box (interquartile) represent the 25th and the 75th percentile, respectively. The line within the box corresponds to the median and the cross to the mean of the distribution, while the whiskers indicate the highest and the lowest SARS-CoV-2 RNA copy values, except for the outliers that are represented by the rounds outside the whiskers.