Wastewater-based surveillance is an efficient monitoring tool for tracking influenza A virus in the community

Abstract

AbstractAround the world, influenza A virus has caused severe pandemics, and the risk of future pandemics remains high. Currently, influenza A virus surveillance is based on the clinical diagnosis and reporting of disease cases. In this study, we apply wastewater-based surveillance to monitor the incidence of the influenza A virus at the population level. We report incidence data of the influenza A virus in 10 wastewater treatment plant catchment areas covering 40% of the Finnish population. Altogether, 141 monthly composite influent wastewater samples (collected between April 2020 and May 2021) were analysed from supernatant fraction using influenza A virus specific RT-qPCR method. During the study period, an influenza A virus epidemic occurred in two waves in Finland. This study shows that the influenza A virus can be detected from the supernatant fraction of 24 h composite influent wastewater samples. The influenza A virus gene copy number in wastewater correlated with the number of confirmed disease cases in the Finnish National Infectious Diseases Register. The Kendall’s τ correlation strength was over 0.600 in all wastewater treatment plants, save for one, which was 0.459. The strongest correlations were 0.761 and 0.833. Wastewater-based surveillance of the influenza A virus is an unbiased method and cost-efficiently reflects the circulation of the virus in the entire population. Thus, wastewater monitoring complements the available, but often too sparse, information from individual testing and improves health care and public health preparedness for influenza A virus pandemics.