By Michelle Roberts
BBC News health reporter, in Washington DC
The world is unlikely to face an explosive Sars outbreak like the one of two years ago, say experts.
Scientists have identified two new coronaviruses
The strain of the virus that jumped readily between humans probably only exists in lab samples, they believe.
It would take an unhappy accident or a fresh mutation of the virus in an animal host for it to re-emerge, a science meeting in Washington heard.
And even if it did, it could be quickly contained, said Dr Kathryn Holmes from Colorado University.
She said scientists had learned a great deal from the epidemic of Sars - Severe Acute Respiratory Syndrome - that began in November 2002 and ended in June 2003.
"Sars is one of the best studied of any emerging infective disease," said Dr Holmes, who has been researching the coronavirus.
"We now have wonderful, very sensitive diagnostic tests and new treatments to fight any outbreak.
"A number of labs have human monoclonal antibodies that neutralise Sars virus.
"These might be used to treat infected individuals or protect the healthcare workers around them.
"There are also multiple vaccine candidates for Sars that have been developed," she told the annual meeting of the American Association for the Advancement of Science (AAAS).
Scientists now know so much about Sars that this knowledge is helping them find and treat previously undiagnosed human diseases caused by other coronaviruses.
They have discovered two new strains - NL63 and HKU1 - which cause pneumonia-like illnesses in children and immuno-compromised adults.
"If an animal strain mutated again we could get an outbreak, but so far as anyone has seen yet, the human epidemic strain is not being harboured in animals."
But Dr Holmes said viruses could be expected to continue to jump from animals to humans, as has been seen recently with avian flu.
"As with the Sars epidemic, we will be protected from these new and emerging diseases by learning as much as possible about all types of viruses in animals and humans."