Hong Kong closed its primary schools and kindergartens this morning, giving more than half a million students a two-week holiday, after the deaths of up to four children amid a flu outbreak.
But while the move sparked concern among parents, both the government and outside experts described it as merely a precautionary measure.
The authorities are thought to be particularly cautious because of the Severe Acute Respiratory Syndrome outbreak in 2003 that killed almost 300 people and brought ordinary life in the territory to a halt. The government was subsequently criticised for not acting quickly enough.
"When you wait until you have all the data, it's too late," York Chow, the health secretary, said today.
He told reporters he had decided to act now in light of the deaths and because a higher proportion of young children seemed to be affected this year, even though the overall level of infection was the same or only slightly higher than usual.
Only two of the children, who died at the same hospital, are known for certain to have had flu.
But Chow said: "If there are two deaths related to flu even before the peak, then we need to do something to minimise the numbers in the weeks to come.
"The scientific recommendation [is] that the incubation period for influenza is usually from a few days to about seven days, so with a stretch of two incubation periods then the school environment should be reasonably free from the virus.
"And if all healthy children go back to school, the chance for cross-spreading should be minimised."
The outbreak has not been linked to avian flu, which has been detected in birds in Hong Kong.
Yuen Kwok-yung, a senior microbiologist who studied the SARS outbreak and has been asked to investigate the latest deaths, said there was no evidence to suggest the virus was more virulent than those in previous outbreaks.
World Health Organisation spokesman Gregory Hartl told Reuters that one of the children who tested positive for flu had an underlying metabolic disease, while the other had encephalitis.
Health officials recorded nine confirmed flu outbreaks and 65 suspected ones in Hong Kong in the last week, mostly at schools.
Just over 532 of the 7 million population have been affected.
"There is nothing exceptional about what's happening in Hong Kong," said WHO spokesman Peter Cordingley, adding that the territory had seen worse outbreaks in recent years.
Almost 1,750 schools and nurseries were closed, affecting nearly 560,000 students. Some families missed the initial closure announcement late on Wednesday and primary schools yesterday took temperatures and handed out facemasks as children arrived.
Officials at the Municipal Centre for Disease Control and Prevention in the neighbouring Chinese city of Shezhen said flu cases had not risen there, but added that they were stepping up public health campaigns on avoiding the illness anyway because it is most common at this time of year.