Researchers have determined the genetic makeup of the virus believed to cause Severe Acute Respiratory Syndrome, or SARS. Scientists say the discovery brings them closer to developing an accurate test for the disease. But a lot of questions remain unanswered.

Researchers in Vancouver, Canada, who have been working around the clock studying SARS, have released a complete genetic blueprint of the virus.

Several centers have been working to read the genetic code, or sequence, of the virus from several patients. A team from the U.S. Centers for Disease Control and Prevention was right behind the Canadians, releasing a nearly-identical sequence. In a teleconference with reporters, CDC Director Julie Gerberding said it is a big step, but not the last step. "Sequencing the virus is a major scientific achievement, and the fact that it has been done so fast and so collaboratively is unprecedented in the history of science," she says. "But it is not the magic bullet for dealing with SARS. We've got a lot of work to do to find treatment, and we've got a long road ahead of us in terms of getting an effective vaccine."

Dr. Gerberding says the sequence will help scientists make tests that are more reliable and quicker than what they are using now. She says the DNA data will help in the effort to develop a vaccine, but a vaccine is still at least a year away.

The genetic data confirms that the virus is a new type of coronavirus, a germ that often causes the common cold in people, and diarrhea in animals. But the new information still does not tell scientists where it came from. The CDC's Dr. Larry Anderson says the virus does not closely resemble any known coronavirus from mice, pigs, or any other animal. "This virus is like a totally separate group -- related, part of the coronavirus family -- but distinct from all the other coronaviruses, both animal and the two human strains," he says.

Researchers say this type of virus has a tendency to mutate over time, becoming more, or less, dangerous. But, responding to a reporter's question, Dr. Gerberding says the fact that some people get very sick with SARS and some do not, does not mean the virus is mutating. "There isn't an infectious disease I know of where there isn't a highly variable clinical picture, all the way from asymptomatic, or mild disease, to sometimes very severe disease."

Dr. Gerberding says it is still unclear whether the people who appear to spread the disease more easily than others are more contagious, or if they just had more contact with other people after they were already sick than people who were quarantined swiftly.