Excreted Tamiflu found in rivers, giving rise to concern about development of resistant strains of seasonal and avian flu
Japanese researchers have found oseltamivir phosphate (“OC”), aka Tamiflu, downriver from sewage-treatment facilities. The source, like that for other drugs that have been found in river and estuarial systems (as noted in prior posts) is urinary excretion by people. The primary concern, of course, is that birds, which are natural influenza carriers, are being exposed to waterborne residues of Tamiflu’s active form and might develop and spread drug-resistant strains of seasonal and avian flu.
The researchers sampled water discharged from three local sewage treatment plants and water at several points along two rivers into which the treated water flowed. Sampling started early in December 2008, as flu season got underway. The researchers sampled again at the height of the seasonal flu’s onslaught in early February, and again as infection rates waned. Residues appeared only during the second sampling, from low nanogram levels at most sampling points to a high of 190 ng/L in a portion of the Nishitakase River where treated sewage accounts for 90% of the river flow.
Computer modeling by the Helmholtz Center for Environmental Research in Germany has shown that OC should survive sewage treatment, a finding now confirmed by the Japanese researchers. The German’s data show that once exposed to sunlight, OC will break down, albeit slowly; the half-life is likely to be about three weeks.
If correlations predicted by earlier studies are correct, concentrations measured at some river sites in the new Kyoto study seem high enough to lead to antiviral resistance in waterfowl, note the researchers.