A day later, when it was clear that this wasn't a case of Sars II, or indeed anything out of the ordinary in flu season, the recriminations began.

Were the school closures and emergency measures a justified response or an overreaction?

And for the government, was it a case of damned if they did and damned if they did not?

The latest flu crisis had its origins on March 1, when three-year-old Ho Po-yi, feverish and coughing, was brought to Tuen Mun Hospital emergency room. After a consultation, doctors believed she should be all right and discharged her. Hours later, after taking afternoon tea, the girl became very sleepy before losing consciousness.

She was already in cardiac arrest by the time she reached the accident and emergency department at Tuen Mun, the hospital said. Less than 24 hours after developing flu-like symptoms, Po-yi was dead.

More were to follow. On Tuesday, seven-year-old Law Ho-ming was taken off life-support at Tuen Mun Hospital. He had been admitted semiconscious with a respiratory disease last Saturday, two days after being discharged from the hospital's emergency room. Around the same time, Prince of Wales Hospital revealed that a 27-month-old boy, Or Ho-yeung, had died hours after being admitted with fever and vomiting on February 26.

The deaths of the three children sparked a chain of events that led to the decision to close schools until March 28 to prevent the spread of flu. Authorities will decide if the closure will be extended beyond that.

An expert team investigating the three deaths, headed by Professor Yuen, has said that while the two children who died at Tuen Mun Hospital had the flu, other health problems may have contributed.

On Friday, the Centre for Health Protection said test results from Po-yi and Ho-ming confirmed no new flu virus was involved in their deaths.

Not since the Sars outbreak have schools closed in response to an outbreak.

Hong Kong is at the height of the flu season but for days last week, Thomas Tsang Ho-fai, controller at the Centre for Health Protection controller, insisted this year's flu was no more severe than last year's or that in 2006. Yet a series of contingency measures was put in place; steps that were not even contemplated in 2006 and 2007.

The measures, announced on March 6 following the death of Po-yi, included shortened visiting hours in public hospitals, daily announcements of outbreaks and a public-education campaign. On Tuesday, the STFA Ho Yat Tung Primary School - the school of the seven-year-old who died at Tuen Mun Hospital - was ordered closed after 35 of its 700 students fell ill with flu-like illnesses.

By Wednesday morning, three schools - Yuen Long Public Middle School Alumni Association Primary School, AD&FD POHL Leung Sing Tak College in Yuen Long and YLPMSAA Tang Siu Tong Secondary School in Tin Shui Wai - had said they were following suit.

At that time, all schools were asked to provide daily reports to the Education Bureau on the number of students who took sick leave and were admitted to hospital with flu.

At the same time, the Hospital Authority would pass information on flu patients to the Health Department, so that it could follow up on the cases and adopt appropriate measures.

The Secretary for Food and Health, York Chow Yat-ngok, appealed for calm, saying he was aware the public would like correct information on infectious disease outbreaks. He urged Hongkongers to understand the situation 'and make decisions accordingly'.

That day, the Education Bureau had organised two seminars for primary school principals on prevention of flu. Asked several times whether schools should be closed, the answer from the attending official was 'no'.

At 7pm, Dr Chow called a meeting with Dr Tsang, Professor Yuen, Director of Health Lam Ping-yan, senior officials of the Hospital Authority and a deputy secretary of the Education Bureau. Dr Chow was updated on the situation and the information pointed to slight increases in flu numbers.

After two hours, a decision was made to close all primary and pre-schools.

In announcing the decision, Dr Chow said he hoped the measure would help contain the disease and give schools a chance to be decontaminated. The number of flu cases was showing a gradual increase, and the peak season was expected to continue for a few weeks.

'There is no cause for alarm,' Dr Chow said. 'This is not just a decision on public hygiene, but also one concerning public sentiment.'

His comments, and those from others, indicated the decision was a political one, to ease the minds of parents and schools.

There was no shortage of critics of the decision and government's handling of it.

'The announcement was made by the health chief, not by the Education Bureau. It is weird,' said Ida Wong Wan-chu, principal of SKH Ho Chak Wan Primary School. 'I do agree this is for the benefit of children's health, but the timing is weird. I think the suspension should be on a regional basis rather than the whole of Hong Kong. The sudden decision created panic among parents.'

Another primary school principal, Leung Kee-cheong of the Fresh Fish Traders' School, said the suspension was understandable, but he, too, was unhappy with the timing. 'In my school, only two students were absent. One of the absentees wasn't even sick. I would prefer that the decision-making power lay in our hands because the schools have a clearer picture,' said Mr Leung.

James Sung Lap-kung, academic co-ordinator at City University of Hong Kong, said the school closure was an example of poor co-ordination between government departments.

'The Education Bureau did not show up in the school suspension announcement,' Dr Sung said. 'Suen Ming-yeung, the secretary for education, did not say anything until now. I can tell it was a political decision because making the announcement on Thursday would have affected coverage of the health care reform, which is very important to the government.'

Dr Sung added that the poor co-ordination had fuelled media criticism.

The World Health Organisation, which was being updated daily by the Hong Kong authorities, said it understood the government's decision.

'Because of Hong Kong's past experiences with outbreaks of Sars and H5N1 [bird flu], we could certainly understand the heightened sensitivity to any kind of outbreaks and flu-type events,' said WHO spokesman Gregory Hartl, adding that the school closures were to be welcomed. 'If that is a means of reassuring the public and the breaking of influenza transmissions, then why not?'

Sian Griffiths, director of the School of Public Health at Chinese University, agreed. 'It is a precautionary principle that 'above all, do no harm' and it does no harm to close schools. If the epidemiological pattern is such that in terms of distribution of disease and the children getting it that you need to act, then you need to act.'

She said closing schools in the face of outbreaks was 'routine practice' in many jurisdictions, including Britain.

Professor Griffiths, who co-chaired the Sars Expert Committee that investigated the 2003 outbreak, said: 'When kids are together they risk spreading the infection among themselves. If they're at home they're less likely to spread the infection, and it helps to control the epidemic and decreases the risk of spread.'

The expert panel will take a few more weeks to complete its report on the deaths of the three children.

While the exact causes of death will be up to the coroner's court to decide, the expert panel is expected to shed some light and set out measures on how such deaths can be reduced in future.

How the crisis unfolded

February 26 Or Ho-yeung, 2, dies at Prince of Wales Hospital

March 1 Ho Po-yi, 3, dies at Tuen Mun Hospital

March 6 String of contingency measures announced to cope with flu surges in public hospitals. Government also begins giving daily updates of flu outbreaks in schools and other institutions

March 11 Law Ho-ming, 7, dies at Tuen Mun Hospital

March 11 STFA Ho Yat Tung Primary School, which Ho-ming attended, closes

March 12 All primary schools, special schools and kindergartens ordered closed

March 13 Expert panel says the deaths of three children with flu-like symptoms does not mean Hong Kong is facing a deadly influenza outbreak

March 14 No new flu virus is involved in deaths of two children in Tuen Mun Hospital, gene sequencing by Centre for Health Protection shows. Five secondary schools close early for Easter