More than half a million Hong Kong schoolchildren stayed at home on Thursday after the government shut all kindergartens and primary schools for two weeks to contain an outbreak of flu, Reuters reported. A government-appointed panel of experts is probing the deaths of three children, aged 2, 3 and 7, over the last two weeks. The two older children were infected with seasonal flu, while the cause of illness in the youngest child is unknown. The health scare has not been linked to H5N1 bird flu but the government's decision on Wednesday night to close the schools brought back memories of 2003, when an outbreak of Severe Acute Respiratory Syndrome hit Hong Kong. Health Secretary York Chow said the government closed the schools because the numbers of young children getting infected seemed higher this year. "Our main concern is the infection of young children. The percentage of young children getting influenza this season seems to be higher," he said at a press briefing. "The second is the mortality ... if there're two deaths related to flu even before the peak, then we need to do something to minimise the numbers in the weeks to come," he said, referring to two of the three children -- a girl aged 3 and a boy aged 7. The government disclosed two new cases on Thursday, a 3-year-old boy WHO was in stable condition in hospital and a 21-month-old boy who died in late February after being admitted to hospital with flu-like symptoms. His cause of illness is unknown. Mrs Kwan, a mother of a 10-year-old student, was worried. "You can see that many people in Hong Kong are a bit scared of such viruses. It's not like before when kids would just have regular cough and fever. Now, you just don't know how serious any outbreak might be. I am very worried," she said. Experts say there was no reason to panic. "This year, there seem to be slightly more flu cases. But from what I can see, we get a bad flu year every few years. I don't think it is very unusual or different from previous years," said Leo Poon, a virologist from the University of Hong Kong.