China's leaders on Tuesday finally joined the battle against the Severe Acute Respiratory Syndrome virus. 

American and Canadian scientists said they had independently mapped the genome of the virus, raising hopes a test could be developed quickly.

But with airlines cancelling flights, tourists staying at home and shops and restaurants empty in SARS hotspots like Hong Kong and Singapore, Asian governments are facing their greatest challenge since the 1997-98 regional economic crisis.

The Standard & Poors Rating agency said the impact would cut 0.6 per cent to 1.5 per cent of the gross domestic product in Hong Kong. Singapore's GDP could be 0.4 to 2.0 per cent lower and China's could lose up to 0.5 per cent.

Carried around the world by travellers after first appearing in the southern Chinese province of Guangdong, the virus has infected 3,300 people and killed 144 in more than 20 countries.

In Hong Kong, the government said SARS had killed nine more people on Tuesday and infected another 42.

The latest figures bring the local death toll to 56 and the number of cases to 1,232. 

Chinese Premier Wen Jiabao called on 'the whole nation' to 'work closely together to win the fierce battle' against SARS, and ordered a campaign to scrub down planes, trains, buses, trucks, taxis and office blocks to kill the virus. 

Fearful of a long-term impact on Asia's fastest growing economy, Wen and Communist Party boss Hu Jintao have appeared in major hospitals and met doctors on the frontlines of the battle.

Posters have been plastered around city streets and subways calling on people to wash their hands after wiping their noses, cut down on drinking and smoking and keep face masks handy. 

But the disease is spreading around China, which has ordered airports to dissuade people suspected of having SARS from boarding planes.

The southeastern province of Fujian reported its first cases. Infections in Beijing rose sharply. More cases were logged in Guangdong, which opened its flagship Canton Trade Fair on Wednesday with foreign participation well down.

Northern Shanxi, one of the first provinces to report SARS in travellers from Guangdong, saw an alarming spike in reported cases to 82 since March.

According to the World Health Organisation, SARS would be hard to track in the hinterland, where the health system receives one fifth of government spending but serves 70 per cent of the population.

China, under fire for being slow in reporting the Guangdong outbreak to the international community, is now issuing updates rapid-fire. The health ministry reports cases daily to WHO, while Beijing and Guangdong file separate and often confusing tallies.

Still, scepticism at this sudden transparency remains. Last week, a Beijing military doctor criticised the health minister for covering up SARS cases and said there were at least 140 cases in military hospitals in the capital alone. A WHO team was still waiting to be allowed into them.