The workshop

The EU-WISH International workshop was organized in Dublin, Ireland, on 9-10 September 2025, by UCD and SSI. The workshop included plenary sessions, panel discussions, and breakout sessions. Progress of the EU-WISH Joint Action, which focuses on strengthening wastewater-based surveillance for public health, was discussed and included the perspectives of international stakeholders participating in the workshop.

Day 1 of the workshop focused on prioritization of the wastewater surveillance targets for respiratory viruses and emerging pathogens, antimicrobial resistance, poliovirus and non-polio enteroviruses, and for illicit drugs, chemical substances and health related biomarkers. Day 2 was devoted to discussing integration of wastewater surveillance for public health action.

The organization of this international workshop was a key milestone of the EU-WISH Joint Action, funded under the European Union's EU4Health Programme.  The workshop was attended by 150 participants on day 1 and 136 participants on day 2. Additionally, 58 people joined online for the streamed plenary sessions on day 1 and 43 people joined online on day 2. The attendees represented 35 countries, which, in addition to EU-WISH partner countries, included experts from Nigeria, South Africa, Tanzania, Tunisia, the Philippines, Türkiye, the United Kingdom and the United States. 

The international workshop was successful in bringing together a high number of experts and key stakeholders, including representatives from international organizations, public health institutions, and research entities, to prioritize surveillance targets, explore integration of wastewater-based surveillance data into public health frameworks, and foster collaboration across countries and with stakeholders to address shared challenges in public health preparedness and response.

Future priority targets for wastewater surveillance were discussed in four breakout sessions on day 1. The main outcomes from these discussions are outlined below.

Discussion outcomes

Respiratory viruses

• The selection, scoring and weighting criteria established during the session were closely aligned with those developed in the ongoing prioritization activity carried out since the start of the EU-WISH Joint Action.
• Public health impact and preparedness remain the main drivers of prioritization, as ‘Risk of significant health impact’ and ‘Likelihood of emergence and transmission’ were consistently ranked as the two most important criteria.
• ‘Sustainability of monitoring’ emerged as an additional high-priority criterion to be included in future prioritization exercise.

Emerging pathogens

• The prioritization process was summarized, providing the relevant information of the already performed steps (consensus definition of ‘emerging pathogens’ to be used in the framework of the Urban Wastewater Treatment Directive and selection of a list of highly relevant pathogens for the prioritization).
• During the breakout session, consensus was reached on the three main categories guiding prioritization of emerging pathogens with agreed sub-criteria for evaluation within each category:
  • Relevance to public health: severity of disease, transmission characteristics, efficacy of public health countermeasures, history of significant impact
  • Added value of wastewater surveillance: enhancement of epidemiological understanding, early warning capability, support for public health actions
  • Feasibility: detectability and data representativeness, laboratory readiness, operational feasibility.
• The relative weight to attribute to the three categories guiding the prioritization was also discussed and it was agreed to attribute higher relative weight to relevance to public health and added value to surveillance compared to feasibility.

Key needs for reaching operationalization

Key needs for implementing wastewater surveillance at EU level include sustainable funding, standardized and adaptable surveillance design, infrastructure and human resources, as well as governance and cross-border coordination. Participants called for the establishment of a governance framework and standardized protocols, supported by a formal cross-border communication network.

Objectives and priority targets for wastewater-based surveillance of antimicrobial resistance (AMR)

EU-WISH has addressed AMR target prioritization through mapping current AMR surveillancein member states and by conducting workshops within and beyond EU-WISH. Based on these activities, the following preliminary general approach was suggested to the Dublin International Workshop participants:

• With the objective to determine temporal trends of AMR circulating in the human population, and to identify emergence of new forms of clinically-relevant AMR, surveillance should focus on untreated wastewater influent, with suggested harmonized surveillance targets being quantitative analysis of carbapenem resistant Enterobacterales (most importantly including Escherichia coli and Klebsiella pneumonia, by culture to assess trends) and resistance genes in the wastewater metagenome to assess emergence of AMR.
• With the objective to generate data on human exposure to AMR through surface water, and to study efficiency of wastewater treatment, surveillance is also recommended to include treated wastewater effluent, with a wider range of options for harmonized surveillance targets (to be further determined within EU-WISH and in collaboration with EU-JAMRAI2).

During the workshop, participants generally adopted this preliminary general approach for wastewater surveillance of AMR. Specific feedback and additions were provided for the following points:

• A group of experts favour testing of a panel of resistance genes to monitor temporal trends.
• Characterization of bacterial isolates by for example whole genome sequencing is considered to be important and will be further discussed within the working group.
• It is recommended that temporal and regional adaptations of the priority list are possible in addition to a minimum approach applied across European countries.
• Criteria for selection of wastewater surveillance plants (WWTPs) were discussed, such as a focus on specific WWTP for emergence of AMR at ‘risk’ sites, as well as procedures towards a common SOP. Training needs for AMR testing were also identified.

Current views, specific requirements and limitations of wastewater-based surveillance of polioviruses and non-polio enteroviruses

Public health actions for VDPV

• It was stressed that it is important to develop and implement a poliovirus preparedness plan 
• It is essential to share wastewater derived poliovirus sequences with the World Health Organization (GPL network) to characterize and identify the virus  
• It is important to ascertain which poliovirus strains are circulating

Sampling strategy

• It is recommended to sample wastewater treatment plants serving large populations preferably between 100.000 to 300.000 people
• Sampling strategies should be country specific, i.e., the breakout session did not recommend detailed general sampling rules
• A good balance between bigger and lower size sampling sites is seen as an added value
• At risk populations include those with low vaccination coverage, those receiving a large influx of people from countries with low vaccination coverage and where vaccine-derived poliovirus is circulating
• Composite, grab or passive samplers can be used for targeting smaller areas within the sewerage system
• For grab samples, setting the sampling time at an adequate moment (when most people use a toilet) is the key to allow as good representativeness of the population as possible
• The sampling site location and duration of site’s exploitation are even more important than the choice of the sampling frequency

Adaptation of poliovirus lab protocol(s) 

• External factors affecting the quality of the sample, e.g., heavy rainfall and chemicals that could act as potential inhibitors (e.g., fertilizers) should be taken into consideration 
• Importance of having a process control such as mouse hepatitis virus, another enterovirus, or pepper mild mottle virus (PMMoV)
• Differences in sequences from the same sample, if coming from cell culture or from direct PCR is a fact to know and consider 
• Need to have guidelines more adapted to EU context (CDC guidelines as a good alternative) 
• No consensus with regards to prioritization of non-polio enterovirus D68 and/or A71
• Vaccine derived poliovirus (VDPV) surveillance is prioritized over non-polio enterovirus D68 and/or A71

Providing a comprehensive list of chemical substances, metabolites, population size and health-related biomarkers for urban wastewater monitoring

Illicit drugs, chemicals and health related biomarkers covers a huge number of potential targets that could, in theory, be included in wastewater surveillance. In this breakout session, there was intensive discussion by participants, many of whom have long-term expertise in wastewater surveillance. Many excellent points were raised in relation to prioritization. In general, there was consensus regarding various substance groups and subgroups: their targets, prioritization, as well as potential to include these in routine monitoring. For some substance groups, however, there still is limited scientific evidence regarding feasibility of wastewater surveillance implementation. For successful and evidence-based prioritization, significant contribution and active participation is needed, especially by countries that have experience with national wastewater surveillance programs and routine wastewater-based monitoring for illicit drugs, chemicals and other health-related biomarkers. Co-operation with other wastewater surveillance networks, for example Sewage Analysis Core Group Europe (SCORE), will be highly valuable.

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Photo gallery from the Dublin Day 1 devoted to prioritization discussions