Tests on the recent influenza-A (H9N2) case have ruled out the possibility of human-to-human transmission, Centre for Health Protection Controller Dr Thomas Tsang says.

Speaking on a radio talk show, Dr Tsang said genetic sequencing studies of the virus isolated from a nine-month-old girl recently hospitalised for H9N2 showed all genes from the virus are of avian origin. The results suggested the virus was directly transmitted from a bird to the girl, without mingling with a human flu virus.

As the girl did not contact wild birds before the onset of the symptoms, Dr Tsang said she may have contracted the virus at the Tseung Kwan O market she visited several times with her family.

Noting tests on respiratory specimens taken from a healthcare worker and three children who were in the same cubicle in the United Christian Hospital with the girl in early March were all negative for the H9 virus and her family members have no symptoms, Dr Tsang said the case did not involve human-to-human transmission.

However, he said children with poorer immunity may more prone to the virus as H9N2 cases recorded in 1999 and 2003 also involved children aged below five.

Mild symptoms

On average samples of 40,000 flu cases will be tested a year for surveillance. Dr Tsang said both H5 and H9 viruses are related to birds and can be transmitted from birds to humans, but the former has a mortality rate of 70% while the latter is a mild form of avian flu and its symptoms are similar to common colds and flu.

When asked whether global warming will lead to virus mutation, Dr Tsang said there is no direct link between the weather and virus reassortment, but warm weather will favour the breeding of germs and communicable disease vectors.

Food safety

On the suspected food poisoning of 15 students from a secondary school in Western District, Dr Tsang said investigations point to bacteria as the likely cause, adding that about 10 to 20 food poisoning incidents in schools are recorded a year.

As a 67-year-old woman who consumed stewed grass carp gallbladder on March 19 has had renal and liver impairment, Dr Tsang urged the public not to eat carp gallbladders, adding there have been reports of poisoning after consumption.

He called on people to follow good food hygiene practices as the number of hepatitis-E cases surged in the last decade, from about 10 cases a year in the past  to 20 to 30 cases in recent years.