Respiratory virus wastewater monitoring

The Finnish Institute for Health and Welfare monitors the amount of coronavirus, influenza A, influenza B and RSV present in Finland’s wastewaters.

Wastewater monitoring can be used to detect changes in the prevalence of respiratory viruses in different cities. This helps to anticipate and assess changes also in the population's infection situation.

How is the presence of respiratory viruses in wastewater monitored?

The presence is examined by measuring the respiratory virus  RNA (genome) in untreated wastewater. The samples are collected from the untreated incoming wastewater as a 24-hour collection sample.

The prevalence of respiratory virus in untreated wastewater is reported 1-4 times a month for the wastewater treatment plants in Espoo, Helsinki, Joensuu, Jyväskylä, Kuopio, Oulu, Rovaniemi, Tampere, Turku, Vaasa.

The frequency of monitoring may be changed, or other localities may be included in the monitoring if the epidemic situation so requires.

Currently, approximately 44% of the wastewater produced by the Finnish population is covered by the wastewater monitoring.

An RNA test does not reveal anything about the viability or infectiousness of the virus – it simply indicates if the coronavirus is present in households connected to the sewer network.

In addition, the wastewater samples are not examined to deduce who has the virus, but rather to simply measure the prevalence of the virus in the particular wastewater network area.

The spread of the disease through wastewater is unlikely as the virus does not remain pathogenic in the environment for a long time.

The number of respiratory viruses can be affected by the following factors:

  • Environmental factors, such as the temperature of the wastewater
  • The concentration of materials inhibiting the enzymes used in the PCR-test in the incoming wastewater
  • Delay between sampling and analysis

Results of monitoring

The coronavirus results are updated on sampling weeks on Fridays in the results report, in which the results of the coronavirus wastewater monitoring have been presented for each municipality.

The results are presented in a weekly report on five different tabs:

  • Entire Country
  • Monitored Localities
  • Previously Monitored Localities
  • Monitoring History
  • Data

The first three tabs present results starting from 27 June 2022.  The Monitoring History tab shows results for the period  3 August 2020 - 7 November 2022. The Data tab shows all the results starting from 3 August 2020.

Weekly report for the monitoring of the coronavirus in wastewater

A portion of wastewater samples in which coronavirus RNA is detected are sent for sequencing for coronavirus variants.

Coronavirus variants in wastewater

The results of other respiratory viruses are presented on the following page starting from 31 July 2023:

Influenza A, influenza B, and RSV in wastewater

Influenza A, influenza B, and RS-virus results from wastewater are presented in three panels, divided by localities:

  • The uppermost panel shows the influenza A results
  • The middle panel shows the influenza B results
  • The bottom panel shows the results of RSV

What is the benefit of wastewater monitoring?

Wastewater research offers an exceptional approach to assessing changes on the population level. This type of research works best when repeated at regular intervals: samples can be used to observe city-specific changes in the prevalence of respiratory viruses. The result describes the infection situation of the population in the sewer network area of the treatment plant during the measurement period. Infected persons have been shown to excrete coronavirus into their faeces before symptoms develop. This excretion is estimated to continue for two to three weeks.

Wastewater monitoring covering almost the entire municipal population can provide valuable additional information on the prevalence of the virus when the results of the coronavirus wastewater monitoring during the sampling period are compared with the location-specific infections confirmed in personal testing. Wastewater monitoring may produce an important advance warning for a specific area if coronavirus is detected in a given municipality at a point when no infections have been detected in personal testing.

In this case, the information obtained from wastewater monitoring may serve as an early warning that there are unidentified infected persons in the area and that the virus may be circulating in the population of the area. In such a situation, it may be necessary for the authorities responsible for communicable diseases to pay particular attention to measures to combat the coronavirus epidemic and preparing healthcare for treating an epidemic.

Coronavirus RNA does not remain measurable in wastewater for a long time and the disintegration is faster in warmer water. It is safe to assume that influenza and RSV do not fare any better compared to coronavirus.

Wastewater treatment plants involved in monitoring

Wastewater treatment plants from different parts of Finland are participating in the monitoring work (Figure 1). The following is a list of municipalities in each hospital district whose wastewater treatment plants participate in the monitoring as well as the municipal areas from which the wastewater networks of the treatment plants collect wastewater.
Wastewater treatment plants involved in the monitoring of coronavirus in wastewaters. The monitoring of the coronavirus in wastewaters is carried out at nine wastewater treatment plants once a week and at two wastewater treatment plants once a month.

Figure 1. Wastewater treatment plants involved in the monitoring of coronavirus in wastewaters. The monitoring is carried out at ten wastewater treatment plants.

Municipalities involved in the monitoring

Espoo, Blominmäki

  • Wastewater network municipalities: Espoo, Vantaa (western part), Kirkkonummi, Kauniainen, Siuntio
  • Number of residents within the network: 390,000

Helsinki, Viikinmäki

  • Wastewater network municipalities: Helsinki, Järvenpää, Kerava, Mäntsälä (southern part), Pornainen, Sipoo, Tuusula, Vantaa (eastern and central part)
  • Number of residents within the network: 860,000

Jyväskylä, Nenäinniemi

  • Wastewater network municipalities: Jyväskylä, Laukaa, Muurame, Uurainen
  • Number of residents within the network: 155,000

Joensuu, Kuhasalo

  • Wastewater network municipalities: Joensuu, Kontiolahti, Liperi, Polvijärvi
  • Number of residents within the network: 98 000

Kuopio, Lehtoniemi

  • Wastewater network municipalities: Kuopio

Oulu, Taskila

  • Wastewater network municipalities: Ii, Muhos, Oulu, Utajärvi
  • Number of residents within the network: 200,000

Rovaniemi, Alakorkalo

  • Wastewater network municipalities: Rovaniemi 
  • Number of residents within the network: 55 000 

   Tampere, Viinikanlahti

  • Wastewater network municipalities: Kangasala, Lempäälä, Pirkkala, Tampere
  • Number of residents within the network: 200,000
  • Number of residents within the network: 91 000

Turku, Kakolanmäki

  • Wastewater network municipalities: Aura, Kaarina, Lieto, Marttila, Masku, Mynämäki, Naantali, Nousiainen, Oripää, Paimio, Pöytyä, Raisio, Rusko, Turku
  • Number of residents within the network: 300,000

Vaasa, Pått

  • Wastewater network municipalities: Vaasa, Mustasaari, Maalahti
  • Number of residents within the network: 70 000

Test method to quantify virus RNA 

Coronavirus wastewater monitoring is based on testing the N2 gene region with a PCR test, which indicates the presence of viral RNA. The test was published by the US Centers for Disease Control and Prevention (CDC) and is currently used by many European countries and Australia in monitoring wastewater for coronavirus.

The PCR test for monitoring the coronavirus in wastewater used the DNA standard for determining the amount of RNA between 3 August 2020 and 7 November 2022. The results for this time period are displayed in the weekly report’s Monitoring History tab.

The measurement of the amount of coronavirus RNA has now changed. Quantitation of the  PCR test results is now carried out using the RNA standard instead of the DNA standard, which was not as well suited for the purpose. The weekly report’s Entire Country, Monitored Localities, and Previously Monitored Localities tabs now show results according to the RNA standard.

The monitoring of influenza A is based on testing the M1 gene region, while the monitoring of influenza B utilizes testing NS2 gene region. RSV is monitored by testing the M gene region. These tests are originally published by CDC. RNA standard is used to quantify RNA numbers in the PCR test. 

Further information

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