Initial tests show that 16 mental patients isolated in a Hong Kong hospital with respiratory tract infections do not have the Severe Acute Respiratory Syndrome virus. A girl was isolated in a Taiwan hospital as a possible SARS case has also tested negative.

Hong Kong breathed a sign of relief after 16 patients with SARS-like symptoms turned out instead to be suffering from influenza A.

The 16, mostly patients and staff from the Salvation Army Mental Institute, were isolated Thursday with respiratory tract infections raising fears that Severe Acute Respiratory Syndrome had re-emerged. A girl in Taiwan also was isolated after returning from Shanghai with a higher fever and cough. Tests later showed she was free of SARS.

World Health Organization(WHO)Geneva based spokesman Dick Thompson says that while the news is good, further tests are needed to completely rule out the possible return of SARS.

"Does it mean that they do not have SARS? It would mean that it would be highly unlikely, there is certainly the possibility of co-infections, so there needs to be a bit more continuing investigation," said Mr. Thompson.

The WHO says post-mortem tests will be conducted on a Philippine woman who died Wednesday in Manila after returning from Hong Kong. The woman had apparently been in and out of hospitals with suspected pneumonia.

The U.N. agency says it is also gathering information on a German citizen in a Philippine hospital with SARS-like symptoms.

The reports of possible SARS cases, says Mr. Thompson, is a welcome sign that Asia's health care systems continue on high alert.

"While none of these cases have actually proven to be SARS we find it reassuring that we do get these reports right away. What it means is that there is a very high level of vigilance that continues in the surveillance system," he said.

SARS emerged from southern China late last year, infecting nearly 8,500 people in more than 20 countries. About 800 patients died from the disease.

While scientists have learned a great deal about the virus that causes SARS, including its DNA fingerprint, they still do not know if the virus could make a seasonal comeback. Many respiratory diseases appear when weather turns cooler.

SARS outbreaks in Vietnam, Hong Kong, Taiwan, Singapore and parts of China, were brought under control by massive quarantines and public hygiene campaigns.