The surveillance of municipal wastewater reveals infectious diseases cost-effectively
Wastewater-based surveillance is an effective tool for monitoring the prevalence of infectious diseases circulating in communities. The WastPan project aimed to improve pandemic preparedness through wastewater-based screening. Wastewater contains several pathogens, thus providing an opportunity to monitor the spread of infectious diseases.
The 24-hour composite samples of untreated wastewater from a treatment plant provide information from an extensive population area, encompassing the entire sewage catchment network areas of the sampled wastewater treatment plants. The samples may reveal many pathogens spreading in the area, such as respiratory viruses and enteric pathogens. Such pathogens are released into the sewage system through various bodily fluids of people in the area, including faeces, urine, respiratory and nasal secretions, saliva, and skin lesions. Such contributing people of these pathogens can be in different stages of infection: symptomatic, asymptomatic, pre-symptomatic, or post-symptomatic.
Wastewater-based surveillance of infectious diseases offers a cost-effective alternative to monitoring such pathogens at the population level. A single wastewater sample analysis can provide comprehensive information on the infectious disease situation in the entire community. The costs of analysis of the wastewater sample providing information from the entire population do not differ much from the analytical costs of a single clinical specimen of the pathogen. Monitoring pathogens with a wastewater-based method does cause privacy issues or ethical challenges, as occurs in clinical testing at an individual level. However, wastewater-based surveillance does not provide infection information at an individual level. So, it cannot directly replace the monitoring of current infectious diseases carried out based on direct patient sampling but rather it provides complementary information to the current surveillance system on the infectious disease status at the population level.
Using limited resources efficiently
The WastPan project involved collecting wastewater samples from ten wastewater treatment plants in 2021–2023; this covers about 40 percent of the Finnish population. The project developed wastewater-based environmental surveillance of pathogenic microorganisms and antimicrobial-resistant bacteria.
“The circulation of several pathogens in different locations can be monitored by analyzing wastewater. The precise selection of surveillance targets is needed for efficient use of limited resources. The targeting pathogens for surveillance need to fulfil the epidemiological knowledge gap at the national and regional levels, and such pathogens should have microbiological evidence of occurring in wastewater,” says Tarja Pitkänen, Chief Specialist.
Health authorities and epidemiologists are the main end-users of wastewater surveillance data. Wastewater surveillance should be prioritised to such infectious diseases whose spread must be detected at an early stage to prevent their further spread in communities and which are difficult to detect with other monitoring tools.
“In the WastPan project, we noticed that a single one-litre wastewater sample can play an enormous role in the up-to-date assessment of the infectious disease situation in the community. The evidence-based practice developed during the COVID-19 pandemic can also be utilised in the surveillance for other pathogens”, summarises Senior Researcher Ananda Tiwari.
The study was part of a WastPan consortium project carried out by the Finnish Institute for Health and Welfare in cooperation with the University of Helsinki and Tampere University. It was a three-year project funded by the Academy of Finland, the Ministry of Agriculture and Forestry, the Ministry of the Environment, the Finnish Water Utilities Development Fund and the National Emergency Supply Agency.
More information
Ananda Tiwari
Senior Researcher
THL
tel. +358 (0)29 524 7498
[email protected]
Tarja Pitkänen
Chief Specialist
THL
tel. +358 (0)29 524 6315
[email protected]
