The lessons of Sars, 10 years on

Ten years ago, on March 12, I sent an urgent e-mail to the World Health Organisation. I was in charge of Hong Kong's Department of Health at that time. We were screening more than 50 hospital staff for symptoms in a mysterious outbreak of flu-like illness. I was alarmed for two reasons. First, these were health care workers, the lifeblood of health systems everywhere, and some were extremely ill with pneumonia. Second, the cause could not be identified. The mysterious nature of the outbreak bothered me deeply, as I believed that Hong Kong's laboratories and scientists were among the best in the world. That view was subsequently confirmed internationally as events unfolded in what became a nightmare experience for me, Hong Kong, and the world.

That same day, the WHO used the internet to alert the world to Hong Kong's outbreak and a similar outbreak at a hospital in Hanoi, where 25 staff were acutely ill with pneumonia or severe respiratory illness, and five were in critical condition. Media coverage of the WHO alert was intense, and that set the alarm bells ringing in hospitals the world over. Vigilance - and anxiety - were high.

More bad news came the following day, when authorities in Singapore reported atypical pneumonia in three young women who had recently returned from a stay in Hong Kong.

By March 15, it was clear that the first new disease of the 21st century was spreading explosively along the routes of international air travel. At 2am, the head of the WHO outbreak alert and response team received an urgent call from Singapore. A doctor who had treated the first cases there was attending a medical conference in New York. He, too, had fallen ill with similar symptoms and was flying home. WHO traced the airline and flight details. At a stopover in Frankfurt, the doctor and his two travelling companions were identified and immediately placed under medical care. They would become Germany's first cases. On the same day, Canada reported its first cases of atypical pneumonia.

The WHO issued a stronger alert. It named the new diseases after its symptoms: severe acute respiratory syndrome. The WHO defined characteristic symptoms and asked all travellers to be alert to what it called "a worldwide health threat".

As details about the earliest cases began to emerge, Hong Kong was again in the spotlight. All of the earliest outbreaks, outside mainland China, could be linked to a single location: the ninth floor of Hong Kong's Metropole Hotel. They could further be linked to a single event: a one night's stay, on February 21, by a physician who had treated pneumonia patients at a hospital in Guangzhou. He was admitted to hospital the following day and died soon after. In a classic piece of detective work, Hong Kong's Department of Health epidemiologists linked that brief stay to 13 infections that seeded the outbreaks in Hanoi, Singapore, Toronto and Hong Kong, starting chains of transmission that would eventually affect thousands.

In the four months following the March alerts, Sars closed schools, businesses and some borders. Air travel to Hong Kong and other severely affected areas seemed to halt overnight. Tourism dried up. Consumers stayed at home. Economic losses mounted into the millions and millions of dollars. By the time the outbreak was declared over, on July 5, nearly 8,500 people had been infected and nearly 800 had died.