Swine flu changes could spell trouble
McClatchy-Tribune Information Services
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Published: November 5, 2009
SAN FRANCISCO — As the H1N1 flu virus spreads at breakneck speed, a team of scientists is close behind. They are watching its evolution through a cutting-edge technology in hopes of answering the question: Where did it come from — and where is it going?
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The collection now includes about 100 samples sent from the California Department of Health Services, 100 from Canada and 100 from various sites in Mexico. More specimens arrive every day.
Long ago, scientists had to peer through microscopes to figure out what was killing people — a process that could take 10 to 20 years.
Modern surveillance is improved not only through use of "deep sequencing,” but another novel detection tool called the virochip, designed by the center’s Joseph DeRisi. The technology can study an entire genome at once.
By comparing H1N1’s genetic code with other influenzas, scientists have found a new combination of elements of previously known viruses. Three flu strains — from pigs, birds and humans — combined in one animal to create an unusual "triple re-assortment.”
It’s not known how, when or where this happened. Then it jumped into humans.
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Their lab at the
University of California-San Francisco holds a growing international collection of virus samples. Genetic analysis of each sample will alert researchers to any tiny change that would create a giant problem.
So far, the swine flu virus seems to be evolving slowly. But a small mutation could create resistance to drugs.
The scientific sleuths are most worried about a big genetic leap — such as in 1918, when a mild virus turned deadly, killing 20 million to 40 million people. If such a leap does happen, the lab hopes to detect it early, triggering more aggressive treatment, quarantining and prevention measures.
"So far, we have no evidence that this virus is any more virulent than seasonal flu,” said
Dr. Charles Chiu, director of the Viral Detection and Discovery Center.
Instead, what seems to matter is the immune response of the infected person; while some people’s systems shrug it off, others go into lethal overdrive. There is also new evidence suggesting that co-infection with another virus, such as the common cold, may worsen illness.
"What we’re worried about is the possibility, because it is a fundamentally new virus, that it may mutate into a strain that is more virulent,” Chiu said.
The ambition of the new center is to hunt down viruses whose identities and origins baffle doctors. And its team wants to understand these mystery viruses at the genetic level.
Chiu’s team is watching H1N1’s continued evolution, a gradual accretion of minor mutations called genetic "drift.”
What he’s worried about is a big change called genetic "shift.”
Such a shift could build a virus that is fast-growing, unfamiliar to the immune system — and highly contagious.
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