Blood tests of people who worked with exotic animals in markets in southern China show that a significant proportion apparently had been infected with the SARS virus, suggesting that some people may become infected without becoming ill, World Health Organization officials said Monday.

The findings are from two separate studies of workers in markets in Guangdong province in China, and they strengthen the SARS link between animals and humans, the officials said in interviews.

At the same time, scientists at Hong Kong University announced Monday night that they were developing what could become the first experimental vaccine for severe acute respiratory syndrome. They said they hoped to start testing the vaccine in animals in early June.

The scientists provided few details about the vaccine except to say that human trials of any SARS vaccine would not be started until after findings of animal experiments are known, and perhaps not even then. Preliminary results of the animal experiments will not be known for at least six months, the scientists said.

Last week, scientists in Hong Kong and at the Center for Disease Control in Shenzen, just across the Hong Kong border in Guangdong province in mainland China, reported finding the SARS virus in three species of animals — Himalayan, or masked, palm civets; raccoon dogs; and badgers — bought in a food market in Shenzen. That discovery suggested, but did not prove, that the SARS virus infects animals in the wild, making it virtually impossible to eradicate the disease.

One of the two new studies involved workers in the same market in Shenzen.

Laboratories around the world have been racing to develop vaccines that might be used to prevent SARS in the event that the main control measures of isolating people with SARS and quarantining their contacts fail to stop transmission.

The need to develop an effective human SARS vaccine became more urgent with the discovery that the SARS virus exists outside humans. This left open the possibility that infected animals might be a continued source of infection in humans.

While testing continues so do the economic woes associated with the illness. Two Matsushita factories in Beijing shut down last week, idling nearly 6,000 workers, after Chinese employees fell ill with SARS — the second time the Japanese electronics maker was forced to suspend production.

Ricoh Electronic Technology, the Japanese office equipment maker, also had to close a Beijing factory temporarily this month after an employee came down with SARS. U.S. mobile phone maker Motorola briefly closed its Beijing offices after a case was found there.

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Such closures highlight the outbreak's mounting impact on export industries that drive China's economy.

Even as reports of new cases decline, the potential for longer-term damage is rising as businesspeople avoid China and precautions within the country interfere with work and deliveries.

"The production system is seriously affected. Goods, materials and supplies are not being delivered," says Chen Xingdong, chief economist in Beijing for BNP Paribas Peregrine Securities Ltd.


Contributing: Associated Press.

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