According to Dutch and Swedish researchers wild ducks carry more than a half-dozen different types of avian flu virus.
The researchers say that the ducks, in particular mallards, could be used to provide flu strains in order to produce to a stockpile of potential vaccines against outbreaks in both animals and people.
In a study the researchers were able to confirm the conventional wisdom that wild birds carry the relatively harmless viruses that eventually mutate into highly pathogenic avian influenza.
Anders Wallensten, Albert Osterhaus and colleagues at the Erasmus Medical Center in Rotterdam, Netherlands, Umea University in Sweden, say that because highly pathogenic avian influenza outbreaks in poultry originate in low pathogenic avian influenza viruses, present in waterfowl, surveillance of the influenza A virus in wild birds could function as an early warning system.
The current strain of bird flu called H5N1 has swept through flocks of poultry in southeast Asia and has killed more than 50 people in Asia since August 2003.
It has now moved west into Russia, north into Mongolia and east into Japan, creating widespread alarm.
Experts have long feared that if the virus mutates and acquires the ability to spread easily among humans, it will cause a pandemic that will kill millions.
In their study Wallensten, Osterhaus and colleagues trapped mallards in Sweden and the Netherlands and tested them for avian flu strains.