Avian Influenza: Is there a risk to water supplies?

World-wide concern over the potential for a pandemic outbreak of avian influenza (bird flu) is currently at high levels as isolated human cases of the highly pathogenic strain H5N1 continue to occur in several Asian countries, and birds infected by this virus are recently reported in several countries in Europe.

While avian influenza viruses are transmitted readily between birds, they are rarely transmitted from birds to humans. When humans do become infected, the avian virus is not easily transmitted to other people. To date, there is no evidence of effective human-to-human transmission of the avian strain of current interest, H5N1.

Avian influenza virus can persist and remain infectious in water for prolonged periods, particularly at low temperatures. It has been suggested that the virus may survive in water and ice in cold climates over winter and infect migratory birds when they return to the water body to breed in springtime.

The influenza viruses are recognised as being highly sensitive to disinfectants and detergents. Influenza viruses are more susceptible to i.e. chlorine disinfection than viruses such as Norovirus, Poliovirus or Hepatitis A virus. Therefore water disinfection processes which are designed to inactivate the more resistant enteric viruses are expected to give a higher degree of inactivation of influenza viruses.

In summary, it can be concluded that based on the current knowledge on the issue, water supplies which receive an adequate level of treatment and disinfection to remove human enteric viruses are not likely to pose any risk of transmission of avian influenza even if infected water birds are present in source waters and reservoirs.

More information can be found in Health Steam Issue 40 (December 2005).

You can also contact the GWRC member in your country (see GWRC Members and Organisation).