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Posted on 04/22/2003 9:45:20 AM PDT by CathyRyan

Chinese scientists have sequenced the genetic code of at least four samples of the SARS virus from different patients. Comparison of these genomes will determine whether the virus is mutating rapidly, which in turn will determine how difficult it will be to develop tests and vaccines based on the virus's genes.

The outbreak of Severe Acute Respiratory Syndrome (SARS) began in China in November, but was not made public until March. Now, 243 people have died and over 4200 infected in 26 countries around the world. Some experts fear it may already be too late to contain SARS, for which there is currently no cure.

The biggest challenge facing health officials is the lack of information from China. The country, home to about half the SARS cases, has been severely and widely castigated for its secrecy, but the criticism appears finally to be making an impact.

China has admitted that the virus is spreading into more remote provinces and has dispatched emergency SARS teams. On Sunday, the government raised the official number of SARS cases in Beijing from 37 to 358 and fired the health minister and the mayor of Beijing for covering up the crisis. By Tuesday, suspected cases of SARS in the capital had reached 602.

Nose and throat swabs

The latest gene sequences of the SARS virus were obtained by scientist at the Beijing Genomics Institute and the Institute of Microbiology and Epidemiology of the Academy of Military Medical Sciences. They have now released five sequences on the internet.

A short report on four of the coronavirus samples was also published. The samples came from nose and throat swabs, as well as lung, liver and lymph node tissue removed during autopsies. Three samples were from Beijing patients, with the fourth from a patient from Guangdong, the province where SARS originated.

Four other code sequences have been released by scientists in Canada, the US, Hong Kong and Singapore. All differ by up to 15 "letters" in the 30,000 that comprise the virus. The Chinese scientists note the differences and write that "the virus is expected to mutate very fast and easily". Such slight differences could also be explained by errors in the sequencing process.

However, most of the variations seen so far seem to affect one gene in particular, while 12 more genes show no changes between non-Chinese sequences. This suggests the variants may genuine mutations.

Scientists will now be working to determine whether different strains produce different symptoms in patients and are spread in different ways. In Hong Kong, the group of patients from the now infamous Amoy Gardens tower block were much more likely to suffer diarrhoea and the virus's spread there has been linked to the sewer system. Scientists at Hong Kong University are now sequencing key regions of the virus.

"Dark misgivings"

China's increased openness has given a cautious welcome by the World Health Organization. "We're now much closer to what we always thought was the reality in Beijing," says Peter Cordingley, spokesman at the WHO's Western Pacific headquarters in Manila. "But as for the rest of the country, we have dark misgivings."

New data reveals that SARS now ranges from the densely populated Sichuan province in the southwest to Liaoning in the northeast. "We're very worried about the less accessible provinces, where there is poor health care and poor resources," Cordingley says

. But another WHO official says China is still not revealing some key data. "Without the date of onset for patients, you can't say what the trend of the disease is," Jeff McFarland, a WHO virologist, told AFP. "This is the data that we need to have to fully understand the epidemic."

"To be able to contain SARS, we have to know what is happening in China," says microbiologist John MacKenzie at the University of Queensland, Australia, and a SARS investigator for WHO. "Until the Chinese authorities come totally and utterly clean, they will maintain a sink that will carry on affecting us globally," he told New Scientist.

MacKenzie adds that problems with the flow of information between authorities and the WHO have also been a problem in Hong Kong, particularly in relation to the spread of SARS in the Amoy Gardens housing block. "Details of work on transmission, on what animals, if any, might be involved is still to come out," he says.

On a more positive note, MacKenzie says the draconian quarantine measures have had an impact in Hong Kong and Singapore, the worst affected places after China. Most secondary schools re-opened on Tuesday after weeks of being closed.

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