Real-time Sewage Surveillance for COVID-19 in Dhaka offers early warning of outbreaks

A real time sewage surveillance for SARS-CoV-2 in Dhaka, Bangladesh can detect the virus at least a week ahead of the traditional clinical surveillance can, which relies on testing individual people for COVID-19, according to a recent study by researchers from icddr,b and partner institutes. The findings suggest that sewage surveillance may be an effective and efficient method for monitoring transmission and identifying future outbreaks of COVID-19 significantly in Low-and-Middle-Income-Countries (LMICs).
The study, one of the largest of its kind to date, titled ‘Real-time sewage surveillance for SARS-CoV-2 in Dhaka, Bangladesh versus clinical COVID-19 surveillance: a longitudinal environmental surveillance study (December 2019-December 2021),’ was published in The Lancet Microbe. The study is a collaborative project with the Institute of Epidemiology Disease Control and Research (IEDCR), University of Virginia, Imperial College London, funded by Bill and Melinda Gates Foundation.  
The researchers monitored sewage in Dhaka, Bangladesh, from December 2019 to December 2021 by collecting samples from three areas of Dhaka city. A total of 2073 sewage samples, collected weekly from 37 sites from eight wards with varying socioeconomic statuses, were analysed for the presence of SARS-CoV-2, causing COVID-19 . Currently there are 51 Environmental Surveillance (ES) sites running in 21 wards of Dhaka North and South city corporation area. 
A real-time ES site map of Dhaka sewage comprising the huge informal sewage network of the city generated through this study is now open for all at Also, the analysed data was converted to an easily readable format and presented on a dashboard reporting the clinical COVID-19 cases. The sewage viral load, updated weekly, is now available on IEDCR website. 
The findings show that sewage surveillance data significantly correlated with clinical COVID-19 data, indicating that the method can provide a more reliable picture of COVID-19 transmission within the community. Apart from accuracy, sewage surveillance is unbiased, more cost-effective, requires less manpower compared to traditional clinical surveillance methods and can record both symptomatic and asymptomatic virus cases regardless of clinical testing. 
“This ES will be an important complementary tool to monitor SARS-CoV-2 as clinical testing recedes. As before the pandemic, initially, several sites in Dhaka were up and running for multi-pathogen ES, future studies will focus on ES for multi-pathogen to identify which pathogens are useful to track in wastewater,” said Md. Ohedul Islam, Research Investigator, icddr,b. 
The researchers believe ES for SARS-CoV-2 is a feasible and useful tool for monitoring trends in transmission intensity in a lower-middle-income setting with a converging informal sewage system. The dashboard can be used by public health officials in Bangladesh to monitor disease transmission and aid them in making informed and actionable decisions to contain COVID-19 outbreaks. 
For example, this data could be used to increase localised testing where appropriate, improve messaging to communities, target non-pharmaceutical interventions, and target lockdowns. Furthermore, this surveillance can potentially monitor the impact of vaccination, particularly on the incidence within lower-income populations.