BBC 1/30/04: origins of Sars have been made clearer by a genetic study that traces it back to wild animals in China

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>BBC DAILY E-MAIL: UK EDITION

>Friday, 30 January, 2004, 9:00 GMT 01:00 -08:00:US/Pacific

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>Full story:

>http://news.bbc.co.uk/go/em/-/1/hi/health/3442317.stm

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Science mapping Sars 'evolution'

The origins of Sars have been made clearer by a

genetic study that traces it back to wild animals

in China.

 

As scientists worry about the potential for bird

flu to one day become a major killer, the study

shows how Sars " jumped " to humans a year ago.

 

More than 800 deaths and 8,000 cases resulted

from Sars outbreaks in Hong Kong, China and

Canada.

 

Researcher Dr Chung-I-Wu, from Chicago

University, said it was " disturbing " to watch it

gradually gain virulence.

 

The current Avian influenza outbreak in the far

East is related to Sars only in demonstrating how

so-called zoonotic diseases in animals can cross

to become a threat to human health.

 

Although not easily passed from human to human,

Sars caused a life-threatening respiratory

infection in many cases, and experts are braced

for its return this winter.

 

Researchers are now convinced that Sars made that

jump in late 2002 in the Pearl River Delta in the

Guangdong Province of China.

 

Cross checking

 

They compared the genomes of viruses isolated

early in the emergence of Sars, and compared them

to isolates from later victims of the virus.

 

This showed how the coronavirus which causes the

illness adapted to become better at living in

humans.

 

Two " genotypes " dominated the early phase of the

epidemic - these were roughly comparable with

coronavirus isolates taken from animals in a

market in Shenzen.

 

In the middle phase of the outbreak - including

the " super-spreader " event at a hospital in

Guangzhou in January 2003 - during which case

numbers multiplied, the genetic makeup of the

virus had already shifted.

 

Different versions of the coronavirus

predominated - with one in the hospital and

another emerging in Hong Kong.

 

Within a month, another genotype had emerged,

which persisted to the end of the outbreak in

August.

 

Cell key

 

When scientists examined levels of gene mutations

in one particular gene - called spike - which was

thought to be involved in the ability of the

virus to enter cells, it was found to be

undergoing rapid mutations at the start of the

outbreak, which slowed down after it had refined

its ability to infect humans.

 

Dr Chung I-Wu said: " What we see is the virus

fine-tuning itself to enhance its access to a new

host - humans.

 

" This is a disturbing process to watch, as the

virus improves itself under selective pressure,

learning to spread from person to person, then

sticking with the version that is most effective.

 

" The genetic fingerprints add a whole new layer

to our understanding of the course of events in

this epidemic. "

Story from BBC NEWS:

http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/3442317.stm

 

Published: 2004/01/30 00:50:44 GMT

 

© BBC MMIV

 

 

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