FOR IMMEDIATE RELEASE
3 January 2007
CONTACT: Jim Tobin
919-653-2582
New Study Examines Ramifications of Widespread Use of Tamiflu Report in Environmental
Health Perspectives says proposed heavy use of Tamiflu
to combat pandemic avian flu could lead to resistant strains of the virus
[Research Triangle Park, NC] Widespread use of the antiviral Tamiflu to fight
pandemic avian flu in humans could actually lead to the development of what
public health officials hope to avoid––drug-resistant strains of the virus
in wild birds. British researchers at the Centre for Ecology and Hydrology in
Oxford have released findings in the January 2007 issue of Environmental
Health Perspectives (EHP) that demonstrate how Tamiflu's persistence
in wastewater and river water could affect the waterfowl that drink from those
water sources.
Since the World Health Organization's first warning of an avian flu pandemic
two years ago, nations worldwide have been stockpiling Tamiflu for treatment
and outbreak prevention. The drug, which minimizes flu symptoms and duration,
inhibits the movement of the influenza virus from the cells it infects, and also
helps uninfected people avoid contracting the flu. However, Tamiflu's
active agent, the metabolite oseltamivir carboxylate (OC) would be excreted
into sewers
for several weeks during a pandemic and is expected to withstand biodegradation.
According to the researchers in the current study, once birds drink OC-laced
water from catchments receiving treated wastewater, they could produce Tamiflu-resistant
strains and pass them on to other birds who share the same waters.
The investigators analyzed 11 waterway catchments in the United States and
5 in England using a metabolic pathway prediction system to determine the potential
biodegradability of OC. They also measured wastewater discharges into the catchments.
They estimated the number of clinically infected people in each catchment area
treated with a full 5-day course of Tamiflu with 100% compliance, assuming
that
80% of the ingested Tamiflu was released into sewer systems as OC and that
all of the OC entering each catchment was flushed out in one day.
Their estimates showed a maximum concentration well above that required for
development of resistance in vitro for 62 consecutive days in the arid
Lower Colorado River
catchment area. Overall, the researchers say that because of the lower population
density for many of the U.S. catchments, peak concentrations of OC in a pandemic
would be approximately 10 times less than the concentrations in British rivers.
All but one of the American catchments studied are larger than those in Britain
and, with the exception of the Lower Colorado River flow area, have more available
dilution per person in each given population. There were no specific ecotoxicological
risks from Tamiflu identified at the time the drug was submitted for approval
to the European Medicines Agency. The authors, however, suggest that the ecotoxicological
risk associated with Tamiflu use needs to be reassessed in light of the hundreds
of millions of courses that would be consumed globally during a pandemic.
The authors warn that, with the release of the uniquely structured, biochemically
resistant OC antiviral into river water, "the range of OC concentrations
predicted . . . will have uncharacterized ecotoxicological consequences." They
call for more detailed water contamination modeling, especially in high-risk
areas of the world such as Southeast Asian countries, where there is more frequent
human-to-waterfowl contact and where future use of Tamiflu would be significant.
They also recommend development of methods to minimize the release of OC into
wastewater systems, such as biological and chemical pretreatment in the toilet.
The lead author of the study was Andrew C. Singer. Other authors included
Miles A. Nunn, Ernest A. Gould, and Andrew C. Johnson. The article is available
free
of charge at http://www.ehponline.org/docs/2006/9574/abstract.html.
EHP is published by the National Institute of Environmental Health Sciences
(NIEHS), part of the U.S. Department of Health and Human Services. EHP is an
Open Access
journal. More information is available online at http://www.ehponline.org/.
Brogan & Partners
Convergence Marketing handles marketing and public relations for EHP, and is
responsible for the distribution of this press release.
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