U.S. Lab Isn't Able to Confirm Possible Canadian SARS Case
A leading U.S. government laboratory said it hasn't been able to confirm Canadian findings indicating a possible outbreak of severe acute respiratory syndrome, or SARS, in a Vancouver, British Columbia, nursing home that has stirred concern over a resurgence of the deadly viral infection.
By Antonio Regalado in New York, Elena Cherney in Toronto and Charles Hutzler in Beijing
Amid such concerns, international health experts said Thursday that they are likely years away from knowing exactly whether SARS originated in animals and, if so, how it then leaped to humans -- knowledge that is crucial to developing a vaccine or stamping out the new viral strain. The experts, from several countries, made the prediction following a study they made in China's southern province of Guangdong, site of the initial SARS outbreak last November.
A spokesman for the Centers for Disease Control and Prevention, in Atlanta, said initial tests on samples provided by Canadian authorities hadn't shown signs of the SARS virus. "CDC and Health Canada are exchanging reagents and protocols used in the different tests to investigate the reason for these differences," the CDC spokesman said.
Concerns over a new outbreak of SARS began after numerous patients and staff at a Vancouver-area nursing home came down with respiratory problems.
Though most of the symptoms were mild and cold-like, as opposed to the high fevers and pneumonia associated with SARS, fears were stoked last week after tests by Canada's National Microbiology Laboratory in Winnipeg, Manitoba, found traces of SARS-virus genetic material in the patients, as well as antibodies to the virus in their blood.
Following questions over the results, samples were sent to the CDC for confirmatory tests, which have come out negative for the SARS virus. Four samples that tested positive for SARS antibodies in the Canadian lab also came up negative in tests run in Atlanta, where technicians used a different method, according to the CDC. The CDC didn't say if it was trying to replicate other tests by the Winnipeg lab that had found bits of SARS genetic material in several samples.
"We are still confident in our results," said Frank Plummer, director of the Winnipeg laboratory. He said tests used by the CDC had also produced negative results at his lab, and that more-sensitive methods had turned up the antibodies. Dr. Plummer said he didn't think the results were in conflict.
Altogether, Dr. Plummer's Canadian laboratory detected evidence of the SARS virus in nine people using genetic probes. Positive antibody results were found in some patients, indicating their immune systems had been exposed to the virus.
A specialist from the World Health Organization is at the Winnipeg laboratory, looking into the Canadian findings. "We are working with the Canadian authorities and just trying to determine what this means," WHO spokeswoman Christine McNab said. "This was an unusual finding, and it is something that we need to follow up on because of the potential global implications."
The potential presence of the SARS virus in patients without the severe symptoms of the disease has prompted a number of theories, including whether the virus has mutated into a more benign form. SARS was first identified as a new disease in February. By that time, it was already spreading quickly, claiming 916 lives and sickening more than 7,500 others world-wide.
The hardest hit were mainland China, Hong Kong and Taiwan. Toronto, Canada's biggest city, was the only place outside Asia to report large numbers of SARS deaths. Aside from the deaths and illnesses, the SARS-hit areas suffered severe economic losses from which they are still recovering.
Keeping Close Watch on an Elusive Disease
Meanwhile, a team of international specialists assembled by the World Health Organization said Thursday in Beijing that it would likely take years of research to understand the chain of transmission of the SARS virus. This suggests that research now under way is unlikely to lead to results that could prove helpful to combat SARS should it recur with the onset of the flu and pneumonia season this fall and winter.
Chinese scientists earlier this year found the SARS virus in several animal species, including the masked palm civet and the raccoon dog. But the specialists said Thursday that those test results are inconclusive, and only proved that those animals, like humans, are susceptible to contracting the coronavirus strain that causes SARS. The foreign specialists, joined by Chinese counterparts, this week concluded a seven-day study in Guangdong province, where they inspected farms and markets where wild animals are sold for food, and reviewed Chinese research efforts to date.
The team's mission is to develop an attack plan for identifying the animal population in which the virus may reside and whether it then passes through other species before infecting humans. "It's not a simple task," said Hume Field, a team member and an expert in animal diseases for the Australian government. "We've got a jigsaw [puzzle] here, and we're trying to put the pieces together."
To blunt the impact of any new outbreak in China, the WHO is working with the Chinese government to improve surveillance to detect the virus and to improve control of infections in hospitals, where the SARS outbreak spread rapidly before it was contained. But identifying a SARS virus reservoir in any animal populations will help in decoding its genetic makeup and ultimately in making sure the disease doesn't repeatedly cycle between animals and people, as influenza is thought to do, said the team members.
The WHO experts criticized the Chinese government for lifting this month a ban instituted during the SARS outbreak on the sale of civets and other exotic animal species. Under a new directive, 54 such animals may be sold for use as food or as pets, provided the animals are farm-raised, not caught in the wild. Henk Bekedam, head of the WHO's Beijing office, called the policy change "premature" until China applies the same health regulations to the farm-raised exotic species that it does to chickens, ducks and other domesticated farm animals raised en masse.
Even if SARS doesn't recur this winter, the experts said that the virus could lie dormant and return years later, as has happened with the deadly Ebola virus in Africa or the Hendra virus, which passed from animals to humans in Australia in 1994 didn't resurface until 1999.
"Let's hope it doesn't return," said Dr. Field of Australia, "and if it doesn't return, let's not drop our guard."
Write to Antonio Regalado at antonio.regalado@wsj.com, Elena Cherney at elena.cherney@wsj.com and Charles Hutzler at charles.hutzler@wsj.com
Updated August 21, 2003 1:33 p.m. |
