Wastewater monitoring

Based on the recommendations of the European Commission, Institute BIOR was the first EU Member State to launch official national monitoring for SARS-CoV-2 in wastewater in order to predict outbreaks and trends in Latvian municipalities in a timely manner.

Latvia is one of the few European countries where, during the covid-19 pandemic, a new approach to wastewater monitoring was developed to provide additional information on the virus.

Surveillance Reports on SARS-CoV-2 RNA Levels Detected in Latvia’s Wastewater

Why Wastewater Monitor?

Wastewater monitoring provides valuable data to the Centre for Disease Prevention and Control (CDPC) and other public health institutions for tracking viral epidemiology. Analyzing the spread of SARS-CoV-2 through wastewater helps forecast and monitor virus trends, enabling timely response to outbreaks.

This method allows for the detection of both symptomatic and asymptomatic cases, as well as the identification of potentially dangerous virus variants. In addition, chemical analysis of wastewater offers insights into public health and lifestyle habits.

Wastewater surveillance is also used to assess the consumption of drugs, alcohol, and new psychoactive substances, as well as to support the early detection of infectious disease outbreaks.

IMPORTANT! There is no evidence that contact with wastewater can cause infection — no live virus has been found in wastewater to date.

Implementation and Analysis of Wastewater Monitoring in Latvia

Depending on the national epidemiological situation, untreated wastewater samples are collected up to twice a week from municipal wastewater treatment plants. These samples are analyzed by the Institute of Food Safety, Animal Health and Environment “BIOR” and the Latvian Biomedical Research and Study Centre. The analysis focuses on detecting SARS-CoV-2 RNA and other substances relevant to public health.

This method enables the observation of virus spread across regions and the potential identification of new mutations. Results are published with a delay of several days. Long-term data help track infection dynamics and reveal trends. Wastewater analysis can also be expanded to detect other biomarkers, providing insight into nutrition, public health, and environmental pollution.

Monitoring is conducted in Latvia’s largest municipalities: Rīga, Liepāja, Limbaži, Jelgava, Jūrmala, Rēzekne, Ventspils, Valmiera, Jēkabpils, Salaspils, Tukums, Daugavpils, Bauska, Talsi, and Saldus.

IMPORTANT! SARS-CoV-2 RNA copy numbers cannot be directly compared between cities due to differences in local wastewater systems. It is more meaningful to follow trends within each municipality individually.

Inhibition Observed – During wastewater sample analysis, certain chemical contaminants present in the wastewater can interfere with enzyme activity, specifically reverse transcriptase and DNA polymerase. These enzymes are essential for quantifying SARS-CoV-2 RNA copies. As a result, inhibition can lead to a weaker signal and potentially lower detected RNA copy numbers than are actually present in the sample.

14-day Cumulative Incidence per 100,000 Population (by Municipality)
This indicator reflects the number of newly confirmed COVID-19 cases in a municipality over a 14-day period, including areas outside the city where wastewater samples are actually collected.

As a result, the reported case number is an approximation. The graph also shows the proportion of the municipal population that is actually connected to wastewater treatment plants included in the monitoring system (typically located in urban areas).

Not Detected (SARS-CoV-2 RNA copy number = 0)
No presence of SARS-CoV-2 was detected in the wastewater sample collected from the treatment plant.

SARS-CoV-2 RNA Detected Below Quantification Limit
A small amount of SARS-CoV-2 RNA was detected in the wastewater sample. While the concentration exceeded the detection limit of the analytical method, it remained below the quantification threshold.

SARS-CoV-2 RNA Copies per 100,000 Inhabitants per Day
The number of SARS-CoV-2 RNA copies found in a wastewater sample, normalized to the population connected to the specific wastewater collection and treatment system, as well as the volume of wastewater treated at the time of sampling.
Normalization is necessary to allow comparison of results across different locations.

5-Sample Moving Average
A trend indicator showing changes in virus presence and potential infection levels. It is calculated as the average of five consecutive measurements — including two before and two after the current data point — of SARS-CoV-2 RNA copies in the wastewater sample.