Potential risks associated with the proposed widespread use of Tamiflu

The threat of pandemic influenza has focused attention and resources on virus surveillance, prevention, and containment. The World Health Organization has strongly recommended the use of the antiviral drug Tamiflu both to treat and prevent pandemic influenza infection. A major concern for the long-term efficacy of this strategy is to limit the development of Tamiflu-resistant influenza strains. However, in the event of a pandemic, hundreds of millions of courses of Tamiflu, stockpiled globally, will be rapidly deployed. Given its apparent resistance to biodegradation and hydrophilicity, oseltamivir carboxylate (OC), the active antiviral and metabolite of Tamiflu, is predicted to enter receiving riverwater from sewage treatment works in its active form.

Our objective in this study was to determine the likely concentrations of OC released into U.S. and U.K. river catchments using hydrologic modeling and current assumptions about the course and management of an influenza pandemic.

We predict that high concentrations of OC (micrograms per liter) capable of inhibiting influenza virus replication would be sustained for periods of several weeks, presenting an increased risk for the generation of antiviral resistance and genetic exchange between influenza viruses in wildfowl. Owing to the apparent recalcitrance of OC in sewage treatment works, widespread use of Tamiflu during an influenza pandemic also poses a potentially significant, uncharacterized, ecotoxicologic risk in each affected nation's waterways.

To gauge the hazard presented by Tamiflu use during a pandemic, we recommend a) direct measurement of Tamiflu persistence, biodegradation, and transformation in the environment; b) further modeling of likely drug concentrations in the catchments of countries where humans and waterfowl come into frequent dose contact, and where significant Tamiflu deployment is envisaged; and c) further characterization of the risks of generating Tamiflu-resistant viruses in OC-exposed wildfowl.