Hong Kong’s government ordered more than half a million primary and kindergarten students Wednesday to stay home for two weeks because of a deadly flu outbreak. It seems that the precautionary measure is effective in containing the seasonal flu outbreak.

"I think this year we probably have a little bit more seasonal flu, perhaps more widespread," Dr. Yuen Kwok-yung, a Hong Kong University professor, told Time. "But it's not more virulent."

AP reports that there were nine new flu outbreaks Thursday, but on Friday only one new outbreak was recorded. The government also asked a few days ago one of the territory’s top scientists to investigate the deaths of three children. AP reports that gene sequencing confirmed they did not contract flu strains deadlier than the ones already circulating.

The government’s decision to close the schools brought back memories of 2003, when an outbreak of Severe Acute Respiratory hit Hong Kong. SARS affected more than 8,000 people between November 2002 and July 2003 in what the World Health Organization deemed a “global threat.” Nearly 800 of those who contracted the disease died from it.

A new US study on the Influenza viruses, published recently in the journal Nature Chemical Biology, has shed light on why winter is the flu season. The research, conducted by the National Institute of Child Health and Human Development (NICHD), one of the National Institutes of Health, has found out that viruses which cause flu coat themselves in fatty material that hardens and protects them in colder temperatures.

This gives them an edge in the cold temperatures of the winter season. The special insulator coating melts in the lungs and the virus is freed to infect the host. This means that if the Influenza viruses are in a warm environment but outside an infectable host, such as is the case in summer, they die rather quickly and can hardly infect another person.