- The Washington Times - Tuesday, May 13, 2003

As the SARS virus continues to spread, research indicates that distinguishing genetic characteristics appear in these viruses from various areas of the world, and scientists hope these differences will allow them to better trace cases of the disease.

“It would be like a sort of genetic fingerprint,” said Ian Simpson, spokesman for the World Health Organization. “If it looks different from different parts of the world, you can tell where it came from. This is a possibility raised by the recent research.”

“If we are unfortunately stuck with the SARS situation as a chronic or long-term problem, … it may very well be helpful in tracing,” said Dr. Arthur Reingold, professor and chairman of epidemiology at the School of Public Health at the University of California at Berkeley.

The specialists cautioned that it is too soon to tell definitively whether this is the case.

The research, conducted by Edison T. Liu and a team of scientists at the Genome Institute of Singapore, appeared in the journal Lancet and was published online Friday. The group looked at the genetic sequencing of 14 different SARS virus “isolates” from around the world, including Singapore, Hong Kong, Vietnam, Beijing and the Chinese province of Guangdong. Among other characteristics, the researchers found genetic differences that put the viruses into two main groups — those originating from the Metropole Hotel in Hong Kong and those in patients from that region, as well as from Beijing and Guangdong, with no association to the hotel.

The research also found genetic differences that “distinguished the Singaporean isolates from all others” and that there “seems to be a signature for the North China” viruses.

The researchers said these differences “might be useful in identifying the differential source of a SARS viral infection.”

They added that it remained to be seen whether these differences caused different symptoms or reactions in patients with severe acute respiratory syndrome.

Dr. William Schaffner, chairman of the department of preventive medicine and a professor of infectious diseases at the Vanderbilt Medical School in Nashville, Tenn., said scientists “need to look at a lot more viruses and see how stable these molecular passport, molecular fingerprints are.” But, he said, “preliminary data indicate we can be somewhat optimistic that this can be an asset to us in the future.”

He noted that scientists have used genetic differences in the polio virus and measles to determine the origin of different cases. If a case of polio emerged in the United States, he said, scientists could look at the makeup of the virus and determine whether it came from Africa or China.

Dr. Schaffner said that if the differences in the SARS virus prove to be reliable over time, this, too, “would help the public health effort in tracking it.”

Scientists generally were not surprised that genetic differences appeared in the SARS viruses examined, because SARS is an RNA virus, and those typically change more than DNA viruses as they replicate.

The virus, however, had not changed as much as some expected. Of the 14 viruses examined, the research team found 129 genetic variations, and 16 that occurred repeatedly.

Dr. Gary Nabel, director of the vaccine research center at the National Institute of Allergy and Infectious Diseases, said there was “a little bit of change, and it’s something to keep an eye on.” But, he added, it is “not something that I would be really worried about at this point from a vaccine perspective.”

Dr. Lee W. Riley, an epidemiologist from Berkeley, said, “Over the next months or years, you’re going to see more differences.”

He said these genetic differences could complicate long-term efforts to produce vaccines — as has been the case with HIV.

But Dr. Schaffner said there is reason to be hopeful. He said the vaccine developed for polio “works the same worldwide,” even though there are genetic differences in the virus in different parts of the world. The same can be said of the measles vaccine, he said.

The SARS virus, he said, is “cleaving more towards the polio and measles model than it is to HIV.”


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