Oseltamivir and zanamivir are the two most prescribed antiviral drugs against influenza in Japan. Oseltamivir and its metabolite are frequently detected in surface water bodies in Japan during the last few years particularly in seasonal influenza period posing a potential threat of emergence of drug-resistant genes in human pathogens. Despite the second largest use of zanamivir as an antiviral drug in Japan, its presence and fate in environmental waters is unknown until now. Accurate assessment on the presence and fates of these drugs in environmental waters is the very first step in countering the potential negative impact on human health. We have recently developed a novel solid-phase extraction (SPE) method for simultaneous recovery of oseltamivir and zanamivir in environmental waters. These antiviral drugs were quantified in Neya River water and a nearby conventional sewage treatment plant (STP) during the 2010/2011 seasonal influenza using the SPE method in this investigation. Oseltamivir and zanamivir concentrations in the river water and STP water samples are discussed and compared with those of the 2009/2010 pandemic influenza in this article. This successful simultaneous quantitation of zanamivir in wastewater and river water with high recovery ratios paves the way for its monitoring in environmental waters.
2012 Japan Society on Water Environment