The World Health Organization has recommended that governments study the SARS outbreak of three years ago in order to prepare for new and possibly more deadly diseases in the future. A new book on SARS, launched in Hong Kong on Thursday, sums up the lessons learned.

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The World Health Organization says the SARS outbreak that emerged in late 2002 caused more fear and disruption than any disease of recent times. Although it killed a relatively small number of people, it had a crippling impact on tourism, trade and the general economy in many Asian countries.

SARS, or Severe Acute Respiratory Syndrome, was defeated after a few months, but the W.H.O. says the world needs to learn the lessons that the disease taught. The threat from communicable diseases remains, as avian influenza - or bird flu - has shown.

Shigeru Omi, the W.H.O.'s regional director for the Western Pacific, says Hong Kong's and China's lack of transparency and public information during the initial stages of the SARS outbreak was responsible for the rapid spread of the virus to much of the world.

Since SARS, he says, governments in the region have become a lot more transparent, including China, the epicenter of both SARS and the avian flu outbreak.

"China in both the health sector and agriculture sector has made a tremendous achievement both in terms of sharing the information and transparency - there is no doubt about it," he said.

Omi spoke at a press conference Thursday to launch a 300-page study of the SARS outbreak, produced by the W.H.O and written largely by those who participated in the battle against the disease.

The W.H.O. says public health systems were undermanned and under-resourced when SARS struck. Omi says many countries in the region have since invested heavily in health infrastructure and research. He says most of the resources, however, have gone to cities, while rural areas are still being neglected.

SARS also put the spotlight on animal husbandry practices in Asia. The W.H.O. still does not know exactly how the SARS virus jumped from animals to humans, but the organization says it was clearly related to the conditions in which animals are kept on the region's markets and farms. Omi says avian flu has highlighted again that backyard farm practices in Asia set the conditions for the emergence of new viruses.

"Raising chickens, ducks and pigs together, often in unhygienic conditions and close to human habitations set the scene for human infections with the new virus," he explained.

Omi says some countries in the region - particularly Thailand and Vietnam, two of the hardest hit by the virus - have made good progress in the fight against bird flu. Vietnam has had no outbreaks in poultry since December and no human cases since November of last year.

But he says the region needs to remain on guard. Even if avian influenza can be contained, he warns, it is likely that the region will see the emergence of new animal driven diseases in the future.