A team of researchers recently discovered that Tamiflu, the leading flu-fighting drug, is accumulating in rivers downstream from sewage-treatment plants in Kyoto. How is this possible? Tamiflu's active ingredient, oseltamivir phosphate, is excreted in the urine of people taking the medication.

Concerns are now building 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 [Science News].

Study coauthor Gopal Ghosh explains that the team took measurements during normal flu season, and found concentrations that

The resistant virus strains would be of the conventional seasonal or avian flu variety, not the H1N1 swine flu strain that is currently pandemic in humans. Seasonal flu, however, kills thousands of people each year.

seem “high enough to lead to antiviral resistance in waterfowl” [Science News].

Computer models show that oseltamivir phosphate will survive sewage treatment, but it should break down when exposed to sunlight and its concentrations should decrease by half every three weeks. The high concentrations were found during a period where 1,738 flu cases were reported in Kyoto, according

to the study, published in the journal

Environmental Health Perspectives. In the United States, Tamiflu is only recommended for the very sick or those with compromised immune system, while Japan has a more liberal policy. Related Content: 80beats: Fish Are on Antidepressants, Allergy Meds, and a Host of Other Pharmaceuticals Discoblog: Prozac Ocean: Fish Absorb Our Drugs, and Suffer for It Discoblog: What You Need to Know About Drug Water DISCOVER: Drugs, From Development to Testing to Marketing to Drinking Water DISCOVER: Italians Find Drugs in River Sewage

Image: flickr / law_keven