PARIS - THE deadly H5N1 strain of bird flu can pass through the placenta of a pregnant woman to her unborn foetus, scientists reported on Friday.

The highly pathogenic flu strain, which has killed 60 per cent of humans infected, can also spread to organs other than the lungs in adults, including the intestines, raising concerns about how the disease might spread, according to a study published in the British journal, The Lancet.

A team led by Mr Jiang Gu of Beijing University studied post-mortem tissues of two adults - one man and a pregnant woman - who had died of the disease.

Since it was first identified in 1997, H5N1 avian flu is known to have infected 328 people worldwide, killing 200, according to the World Health Organisation.

There have been 25 cases and 16 deaths in China, where the virus is thought to have first emerged on poultry farms in the southern province of Guangdong.

Almost all those who contracted the disease dealt extensively with infected fowl, though a few cases of human-to-human transmission have been reported as well.

Scientists fear the virus will mutate into a form that could spread easily among humans, unleashing a pandemic similar to the 1918 outbreak that killed at least 20 million people across the globe.

The researchers detected viral genetic material and antigens not only in the lungs, where the H5N1 strain was known to lodge, but also in the trachea, in disease-fighting T cells of the lymph node, and in brain neurons.

The doctors also found traces of the virus in the placenta, as well as in the lungs, immune cells and liver cells of the foetus.

'This 'vertical transmission' of the H5N1 virus from one part of the body to another and into the womb warrants full investigation, since maternal infections with common human influenza virus are generally thought not to infect the foetus,' Mr Gu said. -- AFP