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The Centers for Disease Control has added SARS to the list of select agents in the United States, a move designed to try to ensure the virus stays within the confines of highly regulated laboratories.

The addition, which the CDC first proposed over two years ago, was given legal status this week when the revised select agent list was published in the U.S. Federal Registry.

The timing of the move is both ironic and co-incidental.

SARS has faded from view since its frightening outbreak was contained mid-way through 2003. Before the virus was brought under control, however, 32 countries reported a total of 8,422 cases and 916 deaths, according to the World Health Organization.

But there has been a resurgence of SARS talk in the past 10 days or so triggered by the World Health Organization's announcement that a newly discovered coronavirus has killed a Saudi Arabian man and severely sickened a man from Qatar. The Qatari remains in critical condition in a British hospital.

SARS is a member of the coronavirus family.

"Should SARS CoV" -- coronavirus -- "be intentionally or accidentally introduced into the population of the United States, as evidenced by the 2002-2003 multi-national outbreaks, the consequences could be significant," CDC spokesperson Jason McDonald explained in an emailed response to questions about the motivation for the move.

Adding the SARS virus to this list means only U.S. laboratories registered with the Federal Select Agent Program can work on the virus.

Laboratories that aren't registered with the program but which have samples of the SARS virus or SARS genetic material must either apply for status with the program, transfer that material to a registered laboratory or provide the program with proof that they have destroyed the material.

One of the key figures behind Canada's SARS fight said the move is a wise one.

"I think there's reason to be concerned and reason to be smart about it. And do you have to go to this length? Well, probably," said Dr. Donald Low, chief microbiologist at Toronto's Mount Sinai Hospital.

Mount Sinai, which treated many SARS patients, for a period had a collection of SARS samples under lock and key in special freezers.

"I don't think we have any left now. I think we got rid of all the tissue and everything," Low said, adding the material was incinerated.

Canada was one of the countries worst hit by SARS, with 375 probable and suspected cases and 44 deaths. Most of the cases occurred in Toronto.

Canada does not have a select agent program. In this country, research with the SARS virus and other disease agents is governed by the Human Pathogens and Toxins Act, which was enacted in 2009. It classifies SARS as a "risk group 3 pathogen". More deadly virus such as Ebola are risk group 4.

During the SARS outbreak, infectious disease experts hoped that if they could halt spread in people, they could stop what was clearly an animal virus from establishing itself in the human population. The idea was to put SARS "back in the box."

The theory proved correct. When scientists learned how the virus spread and hospitals learned how to spot SARS cases, a combination of quarantine for people exposed to the virus and protective gear for health-care workers broke the chains of transmission.

But the virus has reappeared three times since SARS was contained, each time the result of a lab accident. At least 13 people -- six infected in labs and seven contacts of those lab workers -- contracted SARS in three separate lab accidents in the fall of 2003 and spring of 2004. Two of the accidents were in China and the third was in Singapore.

The report on the revisions to the select agent list in the Federal Registry acknowledges that when it first proposed adding SARS, the CDC received a few complaints from universities, public health laboratories and government and commercial facilities.

The critics claimed it would hinder research on the virus, calling the requirements of registering for and complying with the Select Agent Program "an onerous burden."

But other responses supported the move and in the end the CDC pushed on with the proposal. The lethality of the virus -- about 11 per cent of cases died -- as well as the fact there are no vaccines to stop it or drugs to treat it are among the reasons the CDC cited to support its decision.

The arrival on the scene of a new coronavirus may awaken interest in SARS research. And the move to restrict which labs can work on the virus and under what circumstances may reignite criticism in some quarters of the U.S. research community.

But Dr. Michael Osterholm of the Center for Infectious Diseases Research and Prevention at the University of Minnesota said the emergence of the new virus underscores why it is important to be careful with SARS.

"It just points out that coronaviruses can and will likely return ... including the SARS virus. So I think the attention paid to the coronavirus in general is appropriate," he said.

"It's important that we just not let this virus get out again."

McDonald said CDC records suggest 123 entities in the United States had SARS viruses at some point in time.

Of those, 66 are already registered with the select agent program. Of the remainder, only four still possess SARS coronaviruses. "And we are working with them to get registered with the select agent program."

Despite the fact SARS is on the select agent list, U.S. government regulations do not require researchers who work with the virus to do so in the highest containment setting, BSL4 laboratories. Most SARS research can be done in BSL2 labs, though some more dangerous experiments must be done in BSL3, McDonald said.