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Scientists Concerned Antivirals in Treated Waste Water May Lead to Resistant Flu Strains

By Crystal Franco, October 5, 2007

The journal Public Library of Science One (PLoS One) published a research study online on October 3, 2007, raising questions about the potential for influenza A viruses to develop resistance to the antiviral drug oseltamivir (also known under the commercial name of Tamiflu®), due to the presence of the active form of the drug found in post-treatment waste water.1

The article points out that pandemic planning efforts currently count oseltamivir as the primary antiviral treatment, and the drug is routinely used to treat and prevent seasonal influenza. Now, with increasing use of oseltamivir, a new question has emerged as to the “fate of [the antiviral] in the sewage treatment plants and in the environment.”1

According to the PLoS One study, oseltamivir is metabolized by the human liver to produce the active form of the drug (oseltamivir carboxylate [OC]). However, OC is not further broken down in the body, and it is thus excreted into the sewage system in its active form. The authors posit that if OC is not removed by waste water treatment processes, once treated water is returned to the environment, it is possible that avian and mammalian species could ingest OC. The scientists worry that if these species are infected with influenza A viruses, this could provide opportunities for the virus to acquire genetic resistance to oseltamivir.

To assess whether it is possible for OC to be present in the environment, the authors of the study investigated whether OC is removed or inactivated during normal sewage treatment, the authors conducted a series of tests simulating the treatment process. This simulation included 4 steps:

1. Mechanical treatment – filtering of the waste through a grid, then lipids, then sand.
2. Chemical treatment - addition of ferric chloride or ferrous sulfate to remove nutrients
3. Biological treatment – an active biologic sludge which breaks down organic materials
4. UV radiation – simulating the possible degradation of the chemical via sunlight once treated water is released back into the environment (usually rivers, streams, etc.)1

The study found that OC was “not removed in normal sewage water treatments and is not degraded substantially by UV light radiation, and that the active substance is released in waste water leaving the [water treatment] plant.” The authors concluded that the presence of active antiviral in post-treatment water could result in “selection pressures in the environment that favor development of drug-resistance.”

The PLoS One study raises the question of whether the use of oseltamivir and similar drugs should be restricted due to the risk of emerging resistance. The authors conclude by stating that the “effects of pharmaceuticals continuously released into the environment should not be underestimated and certainly investigated carefully.”1

References

1. Fick J, Lindberg R, Tysklind M, et al. Antiviral oseltamivir is not removed or degraded in normal sewage water treatment: implications for development of resistance by influenza A virus. PLoS One;2007:2(10). http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000986. Accessed October 5, 2007.