When Louis Wong came home from work earlier this week his wife brushed aside his attempt to hug their 2-year-old son and sent him straight to the shower.

Hong Kong is on flu alert after the unexplained deaths of four young children with flu-like symptoms. Worried residents are donning surgical masks, flooding hospital waiting rooms and buying up supplies of antibacterial soap as they remember the SARS outbreak that killed 299 people five years ago.

"Everyone in the family has been ordered to take a shower immediately after they've been out,'' said Wong, a 33-year-old father of two and insurance agent at Prudential Plc. "It reminds me of SARS. We're taking the same precautionary measures.''

On Thursday, Hong Kong shut all kindergartens and primary schools, affecting more than 500,000 children. The schools will remain closed through March 28, the end of a scheduled Easter holiday break.

In 2003, severe acute respiratory syndrome decimated Hong Kong's economy and wrecked the tourism industry. People hid behind surgical masks and locked themselves inside their homes, leaving once bustling streets deserted.

The territorial government was criticized for responding too slowly to SARS. This time it isn't taking chances.

In addition to closing schools, the government yesterday named Yuen Kwok-yung, a University of Hong Kong microbiologist who helped discover the cause of the SARS outbreak, to head a panel charged with finding whether flu strains are mutating into a more lethal form.

"When SARS first happened, it was sporadic and no one expected it to become a disaster,'' said Wong, who also has a 6- year-old daughter. "The recent deaths are haunting me.''

Influenza A

The first in the current spate of deaths was that of a 21- month-old boy on Feb. 24, the city's Health Department said. Two of the victims tested positive for influenza A, although the disease hasn't been identified as the cause of their deaths. Two other children died after suffering flu-like symptoms, though tests haven't yet confirmed the presence of influenza A, the subtype that causes seasonal outbreaks of the disease.

The public's initial reaction to the recent deaths has mirrored the response to SARS. Sales of surgical masks at Watsons, Hong Kong's biggest drugstore chain, have increased 11- fold, and sales of flu medicines and antibacterial hand wash have tripled, said Rita Wong, a company spokeswoman.

Calls to the Watsons health hotline have more than doubled, and virtually all the inquiries have been about flu and flu medicines, said senior pharmacist Michael Yim, 30.

Seasonal Outbreak

Rival chain Mannings reported that it only had enough children's masks to last three more days.

"We're sending staff to procure more stock,'' spokeswoman Janet Wong said.

Hong Kong is simply experiencing a seasonal flu outbreak, said Peter Cordingley, the Manila-based spokesman for the World Health Organization's Western Pacific region.

"If you look back to SARS, you can understand why there is a high level of anxiety in Hong Kong among the public at the moment,'' he said. "There is nothing exceptional in what is happening in Hong Kong at the moment.''

The WHO estimates that the flu causes 250,000 to 500,000 deaths a year worldwide.

Several strains of flu and other common respiratory viruses are circulating in the city, said Susan Chiu, associate professor at the University of Hong Kong's department of pediatrics and adolescent medicine. In addition, the disease spreads easily in a crowded city like Hong Kong, with almost 7 million people.

"When people live, work and play in close proximity to each other, the chances of transmitting a virus are higher, and Hong Kong is certainly a densely populated city,'' said Gregory Hartl, a WHO spokesman in Geneva.

Praying for Help

At the Peace Evangelical Center Kindergarten in the suburban New Territories, Principal Wong Siu Lan was so concerned about the outbreak that she gathered her staff together on Wednesday and prayed for the authorities to intervene.

"We started feeling the tension because we constantly have staff and kids calling in sick every day,'' she said.

The government announced its decision to suspend school three hours later.

At Tuen Mun Hospital, where two of the deaths occurred, workers on Thursday handed out masks to the public and placed dispensers filled with antibacterial cleansers at the entrance.

Seven-year-old Lau Man Hay was unaware of the concern swirling around him as he waited with hundreds of others to see a doctor after coming down with flu-like symptoms.

"I'm so happy I don't have to go to school,'' he said.

Louis Wong is less excited. The insurance broker said he's started carrying two surgical masks in his briefcase when he goes to work, just as a precaution.

"I don't believe SARS has gone, and you never know when it's coming back,'' Wong said.