JRC method tells bird flu apart from seasonal flu in wastewater
The European Commission's Joint Research Centre says its digital PCR approach can show whether influenza found in a wastewater sample is avian or seasonal.
AI illustrationThe European Commission's Joint Research Centre (JRC) has developed a laboratory method that can show whether influenza virus found in a wastewater sample is seasonal flu or avian influenza. The JRC said the approach will help national surveillance authorities in the EU monitor pathogens of public-health concern.
According to the JRC, most wastewater tests now used to track seasonal influenza A and B viruses also pick up avian influenza viruses. That makes it hard to tell whether a detection reflects the seasonal viruses spreading among people or potentially concerning bird flu strains.
The new method is a dual duplex (digital) PCR approach. It pairs the CDC Flu SC2 assay, which detects influenza viruses broadly, with the JRC-HA/JRC-MP duplex method, which separates avian from seasonal viruses. The JRC developed that duplex in 2025. It runs two tests at the same time: JRC-HA targets the genetic material of highly pathogenic avian influenza (H5N1 clade 2.3.4.4b), while JRC-MP targets a conserved part of the influenza A genome to confirm that an influenza virus is present.
The JRC said the combined assays can detect seasonal flu and spot the avian virus simultaneously, even when both are in the same sample at very low levels. It added that the approach complements existing clinical and veterinary surveillance. The method is already being applied in wastewater surveillance in Lombardy, northern Italy.
For the study, the JRC worked with the EU Reference Laboratory for Avian Influenza and Newcastle disease, the Istituto Superiore di Sanità and the University of Milan Bicocca.
The work comes after cases of highly pathogenic avian influenza in wild birds rose sharply across Europe from October to December 2025, the JRC said, leading to widespread outbreaks on poultry farms and spillover into mammals. The virus kept circulating over the summer, though at a lower rate. The JRC said the risk of transmission to humans remains low, but that continuous monitoring of the virus's evolution is essential.
The revised Urban Wastewater Treatment Directive requires EU Member States to monitor selected pathogens of public-health concern, including influenza viruses, through their national surveillance systems. Because influenza viruses move between people, animals and the environment, the JRC said, sensitive wastewater tests can serve as an early warning system and help health and veterinary authorities respond faster.