SARS Genetic Code Identified
By Laurie Garrett
STAFF WRITER
April 15, 2003
Two laboratories in the United States and Canada have figured out the complete genetic code of the virus suspected of causing the respiratory disorder SARS, a step essential to developing diagnostic tests and treatments.
The findings are remarkable because of their speed - by comparison, it took nearly three years to find the virus that causes AIDS and another two years to determine its full genetic sequence - and their almost letter-for-letter similarity. The CDC's genomic sequence is longer than the Canadians' by only 15 genetic letters, or nucleotides - a mere blip in the virus' total of 29,736 nucleotides. The makeup of a virus is expected to vary slightly by geographic region. But coupled with optimism that the finding can serve as a road map for developing diagnostic tests, drug development and a vaccine is the continuing mystery: The virus is completely different from any known animal or human pathogen, and public health authorities are unable to conjecture where or how it originated.
It has been presumed that the SARS virus mutated from one that infects animals. But both teams concluded that it bears no resemblance to any known human or animal virus, and actually constitutes its own subclass within the coronavirus family.
"We need to go to China [where the outbreak began] and really do the shoe-leather detective work to find out who were the first cases, where did they go, what did they do," and with what animals might they have been in contact, Dr. Julie Gerberding, director of the national Centers for Disease Control and Prevention said yesterday.
She characterized the decoding of the virus as "tremendously exciting," especially because it was accomplished in 31 days. "It's a scientific achievement that I don't think has ever been paralleled in human history."
The CDC's announcement came on the heels of the weekend's genetic sequencing announcement from the British Columbia Cancer Agency in Vancouver. Though researchers the world over are collaborating in efforts to control SARS - to date it has caused 3,169 cases, 144 of them fatal - there was a competitive breathlessness to the Canadian and CDC reports.
The determination of whether the virus actually causes SARS must await identification of an animal that can be infected with the virus. So far, researchers have not been able to infect and produce the disease in animals. Gerberding indicated yesterday that a lab in the Netherlands may soon have promising results in primates.
Labs in Hong Kong, Japan and Europe are working on their own genetic sequences of the virus, and those findings are expected to shed light on geographic differences, perhaps addressing the issue of "super-spreaders" - people who are so contagious that they seem to infect everybody with whom they come in contact. In Singapore, for example, 60 SARS cases are linked to two wards of Singapore General Hospital. Yesterday the Ministry of Health said the outbreak started with a 90-year-old Chinese woman who passed her infection on to her nursing home attendant. The elderly woman died; the attendant and two other family members are hospitalized. Nearly everyone on the two wards who came within a few feet of the elderly woman later developed the disease.
In Britain, authorities confirmed recently that a man who waited for his plane at Heathrow Airport in London apparently caught SARS from a stranger seated near him in the waiting area. The stranger had traveled from Hong Kong.
Copyright © 2003, Newsday, Inc.