Stealth attack: Avian flu is thought to have originated in Chinese poultry farms. Now researchers reveals it can pass across the placenta.
Credit: AFP
PARIS: The deadly H5N1 strain of bird flu can pass through the placenta of a pregnant woman to her unborn foetus, scientists report today.
The find is significant because other strains of influenza virus are not thought to be transmissible in this way.
The highly pathogenic flu strain, which has so far killed 60 per cent of all people who have contracted it, can also spread to organs other than the lungs in adults, including the intestines. This has raised concerns about how the disease might spread, according to a study published today in the British journal The Lancet.
A team led by Jiang Gu of Beijing University, in China, studied post-mortem tissues of two adults – one man and a pregnant women – 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.
Unleashing a pandemic
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 worldwide.
Now, researchers have detected viral genetic material and antigens (toxins that cause an immune reaction in the body, stimulating the production of antibodies) 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 the lungs, immune cells and liver cells of the foetus.
Vertical transmission
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," Gu said.
In humans, H5N1 mainly affects the lower respiratory tract, crippling the lungs ability to take in oxygen and causing respiratory failure. It also causes diarrhoea in 70 per cent of patients.
The fact that viral genetic material was found in the intestine and in faecal samples "suggest viral replication occurred in the intestine," commented pathologists Wai Fu Ng and Ka Fai To of Princess Margaret Hospital in Hong Kong. "This finding could have important implications for infection control," they said.
The pathologists cautioned that laboratory experiments are needed to confirm Gu's conclusion that the virus is able to replicate outside of the lungs.
OM...
OMG I never knew that