Can wastewater testing predict influenza epidemics? One billion people fall ill each year

Influenza affects around one billion people worldwide every year, but an early warning signal of an approaching wave of infections may emerge not in clinics, but in wastewater treatment plants. Japanese scientists have shown that analysing influenza virus RNA in sewage can predict increases in cases up to a week in advance, faster than traditional medical reporting systems.

Influenza virus RNA detected in wastewater

A team of researchers led by Professor Michio Murakami from the University of Osaka collected weekly wastewater samples from three treatment plants in the region over a two-year period. The samples were analysed for the presence of RNA from influenza A and B viruses, and the results were compared with epidemiological data from the same period, from April 2023 to April 2025. The findings were published on 12 May this year in the Water and Environment Journal.

The analysis resulted in the development of a statistical model that allows wastewater data to be used to predict increases in infection rates in the near term. The coefficient of determination reached as high as 86 percent, indicating strong predictive performance. The Osaka researchers were able to estimate the dynamics of influenza A and B infections separately, although these detailed models still require further validation. This is important because not every type of influenza virus poses the same level of public health risk. Influenza B typically causes smaller outbreaks and does not lead to pandemics. The next step is to distinguish trends for different influenza A subtypes and influenza B lineages.

Signal from wastewater treatment plants for hospitals

The Japanese findings represent a breakthrough in monitoring seasonal viral infections, which affect hundreds of thousands of people worldwide each year. According to data from the World Health Organization, around one billion people contract influenza annually, and between 290,000 and 650,000 cases result in death. Wastewater testing can serve as a signal for decision-makers about the need to increase hospital bed capacity, reallocate medical staff, or introduce restrictions to limit transmission.

Michio Murakami, the lead author of the study, emphasizes that since the completion of the research in mid-2025, the new model has been continuously tested and has maintained high effectiveness. Interestingly, the researchers were able to detect influenza A virus RNA in wastewater even during non-epidemic periods. This is an important finding for monitoring pathogen activity in society and evidence that epidemiological data from hospitals and health centres do not provide a complete picture of the situation.

Wastewater testing an increasingly important public health tool

One of the main advantages of the new method is its speed. Wastewater testing results are available within one to two days, and advanced statistical models allow for immediate estimation of the scale of risk. This is far more efficient than relying solely on clinical data, which typically arrives with significant delays.

Wastewater testing is particularly important because it can detect pathogens in asymptomatic individuals and in those with mild infections who recover at home and do not undergo testing. The method ensures patient privacy and is significantly cheaper than testing thousands or millions of people. Many countries already use wastewater surveillance for dangerous viruses, including COVID-19, RSV, and mpox, and the findings from Osaka suggest that this type of monitoring may become a key factor in public health planning.

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Source:
Murakami, M., S. Morikawa, K. Yamamoto, et al. 2026. “Early Prediction of Type-Specific Influenza Incidence Using Wastewater-Based Epidemiology.” Water and Environment Journal 1–11. https://doi.org/10.1111/wej.70060.