Swedish researchers have discovered that the influenza drug Tamiflu (oseltamivir) is not nullified or degraded during sewage treatment. They believe that in countries where Tamiflu is heavily used, there is a risk that its concentration in natural waters can reach levels where influenza viruses will develop resistance to it. This increases the risk that those viruses infecting humans will become resistant to one of the few medicines currently available for treating influenza.
“Antiviral medicines such as Tamiflu must be used with care and only when the medical situation justifies it,” said Björn Olsen, of the Uppsala University and the University of Kalmar. “Otherwise there is a risk that they will be ineffective when most needed, such as during the next influenza pandemic.”
Perhaps more worrying is the potential knock-on effect involving creatures that frequent water bodies. Influenza viruses are common among waterfowl, especially dabbling ducks such as mallards. These ducks often forage for food in water near sewage outlets. Here they could encounter Tamiflu in concentrations high enough to develop resistance in the viruses they carry.
“The biggest threat is that resistance will become common among low pathogenic influenza viruses carried by wild ducks,” explains Olsen. “These viruses could then recombinate with viruses that make humans sick to create new viruses that are resistant to the antiviral drugs currently available.” The researchers advise that the problem must be taken seriously so that humanity’s future health will not be endangered by too frequent and unnecessary prescription of the drug today.