Two groups of scientists, one in Canada and one in the United States, have unveiled almost identical versions of the complete SARS virus genome sequence.
It's good news that the teams came up with similar results, because that means the genome sequences are accurate. But a SARS, or severe acute respiratory syndrome, genetic sequence is not by any means a magic bullet, researchers said on Monday.
The virus has killed at least 106 people worldwide, and infected 2,600 in more than 15 countries.
The genome sequence provides further evidence that SARS is caused by a new form of coronavirus, the same type of virus that causes some forms of the common cold. The genome data might eventually lead to more accurate diagnostic tests, but they are several weeks away from being widely available, the Centers for Disease Control and Prevention director said on Monday. A vaccine is still at least a year away, and the genome sequence also did not immediately give researchers a clue as to how and where the virus originated.
"Unfortunately, comparing it to animal viruses has not given us any real leads," said Dr. Julie Gerberding, director of the CDC. "We can't say it's mouse or pig (or other animal) yet because it's not similar enough (to any animal viruses) to draw those conclusions."
Both the Canadian and American sequence data is available for free online.
But Henry Niman of Harvard Medical School said the new data shows that part of the SARS genome is similar to certain avian viruses. That jibes with earlier reports that SARS may have jumped from bird to human.
"I was playing around with the sequence, and at the far right-hand end is a sequence that's also found in two avian coronaviruses," Niman said. "Thirty-two nucleotides are exact matches between the SARS coronavirus, avian bronchitis virus and turkey coronavirus."
That's potentially significant, he said, because the sequence had only been found in these two avian coronaviruses up until now. It has never before appeared in a mammalian coronavirus.
Another interesting point, Niman said, is that nearly every member of another family of viruses, called astroviruses, contains this particular sequence. Astroviruses occur in birds, pigs, humans and other mammals. That could mean that this new coronavirus originated when a coronavirus combined with an astrovirus at some point in recent history.
Viruses that emerge by jumping from animals to humans are often quickly contained because they can't be passed from human to human. But SARS has proven to be so difficult to control because humans can pass it to each other fairly easily -- when someone sneezes or coughs and another person inhales infected droplets, or when a person touches something that's been contaminated.
"The last major human to human virus is HIV, and (SARS) is worse than HIV as far as being contagious because all you have to do is sneeze to pass it along," Niman said.
But researchers hope that unprecedented international cooperation and speedy scientific advancement will allow them to quickly control the virus.
"We're only 31 days into the investigation and we have an international collaboration, we've identified the likely cause and also sequenced the virus and created a number of diagnostic tests," Gerberding said. "This is a scientific achievement I don't think has ever been paralleled in our history."
While the United States has seen a milder outbreak than other countries, with about 193 SARS infections and no deaths, reports from China on Monday said the country is becoming more and more alarmed by the spread of SARS. On Monday, China added 11 more people to those who have died from the disease.
Chinese President Hu Jintao visited hospitals in the southern province of Guangdong, the hard-hit region where researchers believe SARS originated. "Since the discovery of the SARS cases, I feel very worried. I feel anxious for the masses," Hu was shown telling medical workers on state television.
State media quoted Premier Wen Jiabao as saying the situation "remains grave" and warning that China's economy, international image and social stability could suffer.
Even though the effect of SARS in the United States has not been nearly as grave, Gerberding said officials can't let down their guard yet because the situation could worsen at any time.
"We have to remain vigilant because it is only one highly transmissible patient that can infect a very large number of people," she said.
One patient in China spread SARS to more than 120 people, Niman said. Experts refer to patients who seem to be extremely contagious as super spreaders.
"Even though we would like to take a deep breath and relax a little bit here," Gerberding said, "this is absolutely not the right time to do that."
The Associated Press contributed to this report.
