An analysis of sewage will be used as an early warning system for the prevalence of Covid-19 in the community.

The Health Protection Surveillance Centre (HPSC) has published its first weekly analysis of Covid-19 in sewage.

It shows the virus is strongly present in all parts of the country and that its prevalence is growing. Since monitoring began in May, the number of wastewater facilities showing high levels of Covid-19 in the community has increased from 13 to 67 in August.

Hospital Report

All 67 wastewater facilities tested by the HPSC showed evidence of Covid-19 in the community. The 68 facilities that are being monitored supply water to 84 per cent of people in the State. Shanganagh in south Dublin did not report for the first week of the monitoring.

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Particles of the virus are to be found in human waste, though the virus is not known to be transmitted through wastewater, and the viable virus has never been detected in untreated or treated sewage,

However, higher levels of Sars-CoV-2 in wastewater suggests more people with Covid-19 infection in the wastewater catchment area.

HPSC national director John Cuddihy said wastewater monitoring will act as a "sentinel" or early warning system for Covid-19 in the community.

He described it as a much more cost-efficient system for monitoring Covid-19 in comparison with community testing – which is more expensive and slower.

Wastewater analysis is also more efficient as many people who have the virus are asymptomatic or do not come forward for testing.

He described it as an “internationally recognised tool in many governments’ efforts to assess the rate of infection across the population, both as a whole and within individual communities,” Mr Cuddihy said.

“Analysis of Sars-CoV-2 genetic material in wastewater captures both symptomatic and asymptomatic people. As such, it helps evaluate how effective specific public health measures are, and can be an important early warning sign of increasing Sars-CoV-2 activity in the community.

“It can also help inform those locations in which increased and enhanced Sars-CoV-2 testing and preventative measures might be of benefit,” Mr Cuddihysaid.

Although wastewater analysis is of limited use now with such a prevalence of the virus across Irish society, it will be useful in the future when numbers abate in determining hotspots of the virus where infections may be on the rise again.

The HPSC monitoring scheme followed a pilot study, funded by Science Foundation Ireland and the Ireland Wales Programme 2014-2020 through the European Regional Development Fund.

It involved three wastewater treatment plants and showed a very close correlation between the presence of the Sars-CoV-2 genetic material and the daily number of new Covid-19 cases.

The samples are analysed at the UCD School of Biomolecular and Biomedical Science. Irish Water and the HSE are also involved in the collaboration.