Hong Kong health authorities tried Thursday to calm public fears over a flu outbreak which has left four children dead and led the city to close all primary schools and kindergartens.
It was the first time schools in this Chinese city have been closed for a health scare since the 2003 SARS epidemic.
The order came late Wednesday, just hours after a flu-like illness was reported in nearly two-dozen schools.
"It was quite a difficult decision but we realise the number of infections is increasing," Health Secretary York Chow told a news conference on Thursday morning, when the closures took effect.
"It's not something based entirely on public health data at the moment. But I think the public would appreciate that what we are doing might be a little drastic -- but it's reassuring to the community," he said.
All primary schools, kindergartens and nurseries in Hong Kong were shut down. But the announcement came too late for many parents, who turned up at closed schools on Thursday morning with their children in tow.
The outbreak has conjured memories of Severe Acute Respiratory Syndrome or SARS, a pneumonia-like virus that killed almost 300 people in Hong Kong five years ago and set off international health concerns.
A seven-year-old boy who died Tuesday after suffering respiratory problems tested positive for a flu strain known as Influenza A or H1N1 -- a virus which was also found in a 21-month-old who died last month.
Two other children have died after suffering flu-like symptoms, and a three-year-old currently in hospital has also tested positive for Influenza A.
On Wednesday, health authorities reported outbreaks of flu-like illness in 23 schools and kindergartens/childcare centres involving 184 people.
The Centre for Health Protection followed up on 50 new reports of outbreaks affecting 305 people Thursday, according to the Government Information Service (GIS).
These included 27 primary schools and 16 kindergartens/childcare centres, GIS said.
Chow said there was no indication that the strain was more virulent than the usual flu virus, and said that the Hong Kong government had decided not to formally inform the World Health Organisation about the situation.
"Since we do not have evidence that there's significant viral change... we would not inform the WHO simply because it's our decision (to close the schools)," he said.
"(But) we cannot wait for the figures to get bigger before we make any decision. We have to make certain assumptions that if there are now two deaths related to influenza... then we need to do something."
Under international health regulations, all WHO members are required to report to the organisation threats to international public health, but the Hong Kong case was not a threat in that respect, WHO said.
Peter Cordingley, a WHO spokesman for Western Pacific, welcomed the Hong Kong government's measures.
"This is not a matter to inform the WHO. It's a seasonal influenza; it's nasty, that's all it is. It's not SARS-related or bird-flu related. It happens every year," he said.
He dismissed suggestions the government was overreacting, saying Hong Kong was understandably on edge after it was "paralysed" by the SARS outbreak.
"It's perfectly normal there should be a high level of public concerns," he said, adding the WHO will monitor the situation.
Schools will be closed for two weeks until March 28 -- twice the incubation period for the virus, Chow said -- but amid worries about the health situation, many parents were angry over how the government handled the closures.
"People have to go to work, we can't just suddenly take a day off or find someone to look after our kids," one angry mother told local RTHK radio. "They should give us one or two days' notice so people can be more prepared."