Odds of avian flu outbreak researched
http://www.canoe.ca/NewsStand/LondonFreePress/News/2005/01/03/805585-sun.html
Scientists want to know how easily the virus can mate with human flu bugs.
HELEN BRANSWELL, CP 2005-01-03 01:55:55
TORONTO -- The alarm now sounds with increasing frequency and urgency: the world could be on the brink of an influenza pandemic sparked by the highly virulent avian flu strain ravaging poultry stocks in Southeast Asia, experts fear. But can that strain -- known as H5N1 -- actually acquire the ability to spread easily to and among people? And if it can, how likely is that dreaded event to occur?
U.S. scientists soon will begin experiments that should provide some answers to those questions. In the process, they hope to learn more about why a virus that nature designed to infect migratory water birds has the astonishing capacity to kill mammal species ranging from house cats to tigers to humans.
The work won't indicate how soon a pandemic might start. And the findings can't be taken as a guarantee the virus will evolve as the science predicts.
"Like a lot of science, it's an imitation of nature," explains Frank Plummer, scientific director of Canada's National Microbiology Laboratory.
"It doesn't replicate exactly what happens. But I think it gives you an idea of the propensity of the H5N1 virus to do this thing."
The researchers, from the influenza branch of the Centers for Disease Control in Atlanta, will mate H5N1 and human flu viruses in a process known as reassortment. Viable offspring will be tested in animals thought to be good surrogates for humans, to see if the viruses can infect, can be transmitted easily from infected animals to healthy ones and to note the severity of disease each provokes.
In other words, researchers will be engineering viruses of pandemic potential. It's high-risk but crucial work, the influenza community insists.
"It's a dangerous experiment," admits Robert Webster, a world-renowned expert on influenza based at St. Jude Children's Research Hospital in Memphis, Tenn.
Still, Webster has no doubt the work needs doing. Science must gain a better understanding of the menacing H5N1 virus.
"These experiments are fully justified, knowing what we know," he stresses.
"This is the worst virus I've ever met in my long career."
The World Health Organization has been pleading for months for qualified research facilities -- of which there are few -- to undertake this work.
The Geneva-based agency would like to be able to put odds on how likely H5N1 is to become a pandemic strain and how deadly -- or not -- H5N1 reassortment viruses might be in humans.
If none of the hybrids causes severe disease, the organization might step down its high level of alert, explains Klaus Stohr, director of the WHO's global influenza program.
REASSORTMENT STUDIES
Scientists from the U.S. Centers for Disease Control will soon begin experiments designed to see how likely it is for the H5N1 avian influenza virus to ignite a human flu pandemic. Some facts about reassortment studies and the work they will undertake:
The aim: To get a better handle on how easy or hard it is for the virus to mate with human flu viruses and create a hybrid capable of infecting people and spreading easily among them.
Secondary goals: By seeing which gene combinations go together in viable and transmissible viruses, scientists may gain some clues about why H5N1 is so deadly. By testing the viruses in animals, they should get a sense of which combinations are particularly worrisome and require heightened responses should they arise.
Method: There are two ways to produce reassortment viruses -- by using a process called reverse genetics or by simultaneously infecting tissue culture with H5N1 and a human flu virus. CDC plans to use both methods.
Reverse genetics: A relatively new technology, this process allows scientists to custom-tailor a virus using a predetermined combination of genes from each of the parent viruses. It is quicker and less laborious than the alternative.
Co-infecting tissue culture: The classical way of producing reassortments, this involves adding H5N1 and a human flu virus -- either H3N2 or H1N1 -- to culture and seeing what grows. It's time- consuming, but more closely mimics what happens in nature.
http://www.canoe.ca/NewsStand/LondonFreePress/News/2005/01/03/805585-sun.html
Scientists want to know how easily the virus can mate with human flu bugs.
HELEN BRANSWELL, CP 2005-01-03 01:55:55
TORONTO -- The alarm now sounds with increasing frequency and urgency: the world could be on the brink of an influenza pandemic sparked by the highly virulent avian flu strain ravaging poultry stocks in Southeast Asia, experts fear. But can that strain -- known as H5N1 -- actually acquire the ability to spread easily to and among people? And if it can, how likely is that dreaded event to occur?
U.S. scientists soon will begin experiments that should provide some answers to those questions. In the process, they hope to learn more about why a virus that nature designed to infect migratory water birds has the astonishing capacity to kill mammal species ranging from house cats to tigers to humans.
The work won't indicate how soon a pandemic might start. And the findings can't be taken as a guarantee the virus will evolve as the science predicts.
"Like a lot of science, it's an imitation of nature," explains Frank Plummer, scientific director of Canada's National Microbiology Laboratory.
"It doesn't replicate exactly what happens. But I think it gives you an idea of the propensity of the H5N1 virus to do this thing."
The researchers, from the influenza branch of the Centers for Disease Control in Atlanta, will mate H5N1 and human flu viruses in a process known as reassortment. Viable offspring will be tested in animals thought to be good surrogates for humans, to see if the viruses can infect, can be transmitted easily from infected animals to healthy ones and to note the severity of disease each provokes.
In other words, researchers will be engineering viruses of pandemic potential. It's high-risk but crucial work, the influenza community insists.
"It's a dangerous experiment," admits Robert Webster, a world-renowned expert on influenza based at St. Jude Children's Research Hospital in Memphis, Tenn.
Still, Webster has no doubt the work needs doing. Science must gain a better understanding of the menacing H5N1 virus.
"These experiments are fully justified, knowing what we know," he stresses.
"This is the worst virus I've ever met in my long career."
The World Health Organization has been pleading for months for qualified research facilities -- of which there are few -- to undertake this work.
The Geneva-based agency would like to be able to put odds on how likely H5N1 is to become a pandemic strain and how deadly -- or not -- H5N1 reassortment viruses might be in humans.
If none of the hybrids causes severe disease, the organization might step down its high level of alert, explains Klaus Stohr, director of the WHO's global influenza program.
REASSORTMENT STUDIES
Scientists from the U.S. Centers for Disease Control will soon begin experiments designed to see how likely it is for the H5N1 avian influenza virus to ignite a human flu pandemic. Some facts about reassortment studies and the work they will undertake:
The aim: To get a better handle on how easy or hard it is for the virus to mate with human flu viruses and create a hybrid capable of infecting people and spreading easily among them.
Secondary goals: By seeing which gene combinations go together in viable and transmissible viruses, scientists may gain some clues about why H5N1 is so deadly. By testing the viruses in animals, they should get a sense of which combinations are particularly worrisome and require heightened responses should they arise.
Method: There are two ways to produce reassortment viruses -- by using a process called reverse genetics or by simultaneously infecting tissue culture with H5N1 and a human flu virus. CDC plans to use both methods.
Reverse genetics: A relatively new technology, this process allows scientists to custom-tailor a virus using a predetermined combination of genes from each of the parent viruses. It is quicker and less laborious than the alternative.
Co-infecting tissue culture: The classical way of producing reassortments, this involves adding H5N1 and a human flu virus -- either H3N2 or H1N1 -- to culture and seeing what grows. It's time- consuming, but more closely mimics what happens in nature.
