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NEW YORK---The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined

< < Back to Start of Article NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that

< < Back to Start of Article NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that

< < Back to Start of Article NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

.

The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

.

Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

.

"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

.

The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

.

"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

.

A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

.

Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

.

In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

.

"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

.

The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

.

The New York Times NEW YORK The first major study of the genome of the SARS virus shows that it has not mutated significantly in its spread to different countries.

.

The findings were encouraging because if the virus remains stable, chances are increased that a vaccine might be developed, the authors and other experts said Thursday. That effort is expected to take years.

.

But the experts said that the findings also meant that SARS, unlike some other new and emerging diseases, had not weakened as it passed through successive generations. Some experts had expressed hope that the virus would cause less severe illness as it spread.

.

Also, in a report on the outbreak in Singapore, the U.S. Centers for Disease Control and Prevention said that five individuals had acted as "superspreaders" in passing the virus to 144 other people, while 81 percent of infected people did not transmit to anyone else.

.

The U.S. health agency defined superspreaders as individuals who transmitted SARS to 10 or more people. Doctors have described superspreaders in other infections like tuberculosis, rubella and Ebola.

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The director of the agency, Dr. Julie Gerberding, said her agency was making available to state health departments the biological material needed to perform a diagnostic blood test. The test detects the antibodies that the immune system forms as it fights off infections; the immune system produces a specific antibody against each microbe.

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Researchers at the Centers for Disease Control have developed a test like the Elisa, which is used to screen for the AIDS virus and other infectious agents. The SARS test is expected to have limited use because it cannot detect antibodies until three weeks after the onset of illness. A positive result would strongly indicate that an individual had been infected with the SARS virus, but a negative test would not necessarily rule out such infection, Gerberding said.

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"Probably the most important lesson that we learned from the Singapore experience" is the need to "remain vigilant," she said. "If we were unfortunate to have someone with unrecognized SARS," who could infect many others, "we could have a cascade of transmission."

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The genome study, by Dr. Edison Liu and his team in Singapore, involved comparing the complete genomes of SARS virus from nine cases there with virus samples isolated in Canada, China, Hong Kong and Vietnam. The study was published in The Lancet.

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"This is the first major analysis of this virus," said Dr. David Heymann, executive director of communicable diseases at the World Health Organization. The Geneva-based agency has overall responsibility for investigating the epidemic, which has affected 29 countries.

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A number of laboratories have also found that the SARS virus has not mutated significantly in the seven weeks since it was detected, Heymann said.

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Dr. Earl Brown, a virologist at the University of Ottawa, said: "I hope that SARS will change, but I'm concerned. This virus seems to be happy with the genes it's got." Brown, in a commentary on the study in The Lancet, suggested that because the SARS virus had changed relatively little in its first few months, it seemed unlikely to mutate into a milder form.

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In an interview, Brown said that if a new virus was going to evolve into a more benign form, it normally did so in the early months of an outbreak, a pattern followed by the Ebola virus, which causes a deadly hemorrhagic fever.

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"Ebola transmits like wildfire in hospitals and among family members for two or three transmissions and then loses the ability to infect people," he said. "It loses the ability to spread and keep its virulence, and burns out on its own."

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The World Health Organization has said that a newly discovered member of the coronavirus family causes SARS. But the agency and other scientists agree that more work needs to be done to be certain.

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The New York Times

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