Carcasses of birds infected with the bird flu virus continue to be infectious for up to two years, a new study has found.

The bird flu virus can survive in landfill leachate — liquid that drains from a landfill — for at least 30 days and up to two years, according to the study that appears in the June issue of the journal Environmental Science & Technology.

Factors that most reduced the virus’ survival times were elevated temperatures and acidic or alkaline pH, said Nebraska public health researchers who conducted the study.

Hundreds of millions of chickens and ducks infected with bird flu have died or been killed worldwide in an effort to control the spread of the disease.

The remains are disposed of in different ways, including burialin landfills. For example, the carcasses of more than 4 million poultry that were culled or died during a 2002 outbreak in Virginia were placed in municipal landfills, according to the American Chemical Society.

‘Data obtained from this study indicate that landfilling is an appropriate method of disposal of carcasses infected with avian influenza,’ concluded Shannon L. Bartelt-Hunt and colleagues, who noted that landfills are designed to hold material for much longer than two years.

But the researchers said the safety of landfill disposal should receive more attention.