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Lessons From Sars Help Combat Threat From Bird Flu

International health officials meeting in Vietnam this week said the bird flu outbreak in Asia poses a grave global threat to public health.

Experts from the United Nations and other health agencies met to discuss ways to prevent a flu pandemic, which officials said was possible if the virus mutated into a more infectious form that could be transmitted more easily from person to person.

Over the last 14 months, the virus has killed at least 45 people from Vietnam, Thailand, and Cambodia - 13 of them since December.

In addition to the human suffering it has caused, the bird flu outbreak has required the destruction of millions of potentially infected chickens, and that has devastated many local economies. Total poultry farm losses in Asia are estimated at more than 10 billion dollars.

Health officials wrapped up their 3-day meeting in Vietnam with calls for reducing infection at its source -- targeting free-range chickens and ducks in order to curb the disease before it spreads.

Joseph Domenech of the United Nations Food and Agriculture Organization says preventing the spread of the virus from poultry to humans is more realistic than trying to eradicate the disease altogether. Controlling the disease, this is something that can be done today because the tools exist, he says. Yes, it is possible with more investment to achieve good results in terms of controlling the effect of the disease.

U.S. Centers for Disease Control and Prevention head Judy Gerberding says the CDC is taking precautionary measures to prevent a new avian strain from spreading in Asia and abroad.

There are more pigs, people, and poultry in that environment than we have ever seen before. That is the formula for emergence of new flu strains, she says. We already know this particular strain of virus can infect people, we already know that it can occasionally move from person to person, and we know how these viruses evolve. So it is a worrisome situation and we are taking many steps to be as prepared as we can and to prevent the transmission of a new virus strain in the global arena.

The U.S. government has ordered two million doses of the vaccine to protect against known strains of the bird flu.

The public health challenge posed by emerging diseases like bird flu was high on the agenda at last week's meeting in Washington of the American Association for the Advancement of Science. Health experts are drawing lessons in their experience with SARS, a potentially deadly respiratory disease which -- like the avian flu -- jumped from animals to humans.

SARS is one of the best studied of any infectious disease. University of Colorado microbiologist Kathryn Holmes says scientists began saving specimens from the onset of SARS in November 2002. People have gone back to look at those specimens that were kept at a time when southern China didn't admit that it had any problem, she says. The specimens were there. Sixty- three genomes were sequenced completely and then you could look at what mutations were necessary to accomplish this jump from animals to humans.

By March 2003 scientists had isolated the virus that causes SARS. It turned out to be a coronavirus, strains of which are associated with the common cold and not usually deadly. An examination of the genetic structure indicated a new type.

Kathryn Holmes says experiments on animals provide valuable insights into human immune response. You can use those models to evaluate the effectiveness of vaccines in preventing re-infection or the ability to clear virus using new drugs that are being developed, she says.

Prior to the SARS outbreak, no human antibodies existed to help fight the disease. As a result, it spread rapidly to 30 countries, prompting a massive public health response that has effectively halted new outbreaks of the disease.

Microbiologist Kathryn Holmes calls the response to SARS a triumph in modern medicine. She says while the likelihood of reemergence is low, if SARS did reoccur, it could be more quickly contained. She says, We have wonderful, very sensitive diagnostic tests, good clinical differentiation now between SARS and other infections. And, she says, There have been a number of labs that have made human monoclonal antibodies that neutralize the SARS virus, and these might be able to be used to treat infected individuals. Or, if that didn't work to protect the health care workers around them.

Several possible vaccines for SARS have been developed. Kathryn Holmes says research on the SARS coronavirus has also helped identify other new human respiratory diseases. One is called Human Coronavirus-NL63, and it causes pneumonia in children and in immuno-compromised adults. Another one was just reported this January from Hong Kong, and it is closely related to a mouse virus and again, it causes pneumonia.

Kathryn Holmes expects viruses to continue to jump from animals to humans. She says the best defense is to learn as much as possible about all types of viruses in both animals and humans, and use that knowledge to minimize the cross-species infections that could someday spark a deadly pandemic.