Wastewater Surveillance
Introduction:
- Sewage or wastewater can tell us about the health of a community.
- Most pathogens like bacteria, viruses, and Protozoa remain viable in the sewage environment for longer periods.
- Wastewater-based health surveillance is an excellent tool for tracking the presence of different pathogens in the environment.
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Testing sewage samples provides a clear picture of virus circulation in the community days in advance of testing infected people. |
Key points:
- Tracking of the COVID-19 pandemic relies heavily on testing symptomatic individuals for the presence of SARS-CoV-2 RNA.
- Many infected people are likely to be asymptomatic and are not tested. This leads to the underestimation of COVID-19 cases.
- Infected people start shedding the virus via the faecal route, or four-seven days before symptoms show up or actual testing.
- The viral load estimated a higher number of cases than the number of reported cases 8-14 days in advance at the citywide level.
- Environmental surveillance captured near real-time virus circulation at the community level.
- The study used real-time genomic surveillance to understand the variants causing the emerging patterns in viral load in wastewater.
Hotspot identification:
- The wastewater samples are monitored to show which variant was causing the increase in cases and identify hotspots in the city.
- Wastewater treatment plants with BA.2.10 or a mixture of BA.2 sublineages showed an increase in viral load and highlighted that there was no new variant behind the surge.
- Comparisons with clinical genomic surveillance data on the GISAID database showed that while the general trend in Variants of Concern(VOC) remained similar, the wastewater genomic surveillance recorded a huge diversity in SARS-CoV-2 lineages dominated by the Omicron family.
- Two Omicron sub-lineages -BA.2.10.1 and BA.2.12 were detected in wastewater.
- The early emergence of a variant in the wastewater implies that a significant proportion of individuals in the community are infected with that variant and shedding the virus.
- A late detection in the clinical sample could happen due to limited or biased testing, sequencing a large proportion of individuals were asymptomatic or home testing upon COVID-19 symptoms.
Poliovirus Eradication:
- Wastewater surveillance played a crucial role in eradicating the poliovirus in India in 2012.
- The environment needs to be scale-up the environmental surveillance beyond poliovirus and SARS-CoV-2 virus to pan pathogen surveillance and integrate with the main healthcare system.
- This kind of surveillance has the power to predict neglected and emerging diseases.
Conclusion:
Our approach and protocols developed lend support to establishing environmental surveillance for monitoring and an early-warning system for detecting multi-pathogens.
