Water: unlikely source of transmission for bird flu

H5N2, a low-pathogenic avian influenza (bird flu) virus is similar to H5N1, however, it is unknown if H5N1 is more resistant than H5N2 to procedures used by the water management industry, according to Araceli Lucio-Forster, lead author and a specialist at Cornell's Department of Microbiology and Immunology.

Because H5N1 requires high-level bio-safety facilities, H5N2 was used as a surrogate virus. Given the similarities, if H5N1 entered the water treatment system "the virus should be inactivated, which means treated water may not be a likely source of transmission," said Lucio-Forster.

UV radiation - To test the effectiveness of UV radiation for killing the H5N2 virus, researchers exposed the virus in drinking water and in wastewater effluents to UV light at varying levels. The treatment was very effective in killing H5N2 at levels within industry standards.

Chlorine - For chlorine, the results were less definitive. Inactivation of H5N2 depends on both chlorine concentrations and time of exposure. US treatment plants typically treat drinking water with chlorine concentrations of 1 milligram per litre for 237 minutes. Given these guidelines, researchers found that H5N2 (and likely H5N1 as well) would be mostly inactivated. Further studies are needed to see if the viruses stay active when they come out of faeces or are at different pH and salinity levels.

Bacterial digesters - The small laboratory-scale study found that bacterial digesters also reduced H5N2 to undetectable levels after 72 hours (consistent with industry standards). The researchers also found that higher digester temperatures inactivated the virus more quickly.

Related links:

Environmental Engineering Science

Cornell's Department of Microbiology and Immunology

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