Children are more susceptible to avian (bird) flu than adults, a new study suggests.

Researchers from the University of Hong Kong and Australia's Adelaide Women and Children's Hospital say the finding could be a "small step" towards finding new ways to treat the infection.

According to the World Health Organisation (WHO), since 2003 there have been 331 cases and 203 human deaths from avian flu, largely in south-east Asia and some Middle Eastern countries.

In the latest study on the disease, the researchers analysed parts of the body that act as 'beacons' for the influenza virus in the upper and lower respiratory tract, including the lung.

They found that the lectin MAA, which binds sugars and identifies the receptor for avian viruses - including H5N1, worked throughout the respiratory tract but was particularly good at binding to children's cells in the lower respiratory tract as well as the upper respiratory tract of adults.

Writing in the journal Respiratory Research the scientists argue that these findings could explain how avian flu infects children more readily than it does adults.

"Understanding the how and why of avian virus infection of humans is a very complex process involving research into properties of H5N1 virus, the host receptor and the cellular response" said researcher Dr John Nicholls.

"We believe that the studies we have done investigating where the receptors are located and their distribution with age is a small step towards unravelling this process and help in finding ways to diminish the potential treat from this emerging infection."