|
| all news articles | by topics |
|
news
articles about singapore's wild places
|
| National
Geographic 5 Oct 05 "Bird Flu" Similar to Deadly 1918 Flu, Gene Study Finds by Brian Handwerk for National Geographic News Scientists have reconstructed the genetic code of the deadly 1918 "Spanish flu," which swept the globe and killed an estimated 20 to 40 million people. Among their findings: The 1918 virus strain developed in birds and was similar to the "bird flu" that today has spurred fears of another worldwide epidemic. By studying the once deadly 1918 virus's genetic information, scientists may become better able to predict future pandemics, or widespread epidemics. It may also aid the development of new vaccines, antiviral medicines, and other treatments to cope with flus. "The purpose was to get at questions relating to the 1918 pandemic," said Jeffery Taubenberger, of the Armed Forces Institute of Pathology (AFIP) in Rockville, Maryland. Taubenberger co-authored one of several related papers in this week's issues of the journals Nature and Science. "How did this particular virus form and get into humans? How did a pandemic start?" Taubenberger said. "Why was this particular virus so virulent? And in a broader sense what can we learn from the lessons of 1918 that can help us in the future?" Influenza viruses were unknown in 1918, so there was no way for doctors or scientists to directly study the flu during or after the outbreak. But some institutions, like the AFIP, preserved tissue samples from 1918 flu victims. Those 87-year-old samples—and others from a victim who was buried in, and preserved by, Alaskan permafrost—yielded tiny fragments of genetic material that were used to piece together the virus's genetic coding signature. The final genes of the virus's genome sequence are being published this week. Scientists used the completed, full viral sequence to create a live virus with the eight viral genes of the Spanish flu, named for an early, devastating outbreak in Spain. Even if somehow released, that virus would be unlikely to cause a pandemic like that of 1918, because humans have likely acquired some immunity in the intervening decades. Nonetheless, it is currently contained at Atlanta, Georgia's Centers for Disease Control and Prevention (CDC) under extremely strict security. A Weapon Against the Next Pandemic? Many experts warn that the world is overdue, and unprepared, for a global influenza pandemic. The next outbreak could well be as deadly as the Spanish flu, also known as H1N1, and potentially leave tens of millions dead. Currently experts can't determine exactly which viruses might spark pandemics, though the Spanish flu data may help to identify which strains bear close observation. H5N1, a strain of avian influenza called the bird flu, is the most likely candidate. The largely Southeast Asian disease is commonly found in birds but also occurs in mammals like pigs, cats, and humans. It has killed several dozen people, but as of yet it cannot be easily transferred from person to person and so has not developed into a pandemic outbreak. Analysis of the 1918 strain revealed several mutations also found in H5N1. The findings suggest that both strains share an ability to jump directly to humans from other animals without having to first combine with a flu strain already adapted to humans. "The sequence evidence from 1918 suggests that the virus is from completely avian origins," said Adolfo Garcia-Sastre, a microbiologist at Mount Sinai School of Medicine in New York City. Human immune systems would likely be caught off guard by a purely avian virus to which they have no acquired immunity. The century's other great pandemics, of 1957 and 1968, were sparked by hybrid flu viruses—human flus that acquired some genes from an avian source. "This [finding] suggests that pandemics can form in more than one way, which is an important point," said the AFIP's Taubenberger. "We've been identifying a series of mutations that we believe are important in the way that an avian virus would adapt to become a human virus," Taubenberger added. Though the evidence is compelling, only pre-1918 samples would allow scientists to be 100 percent sure that no aspects of the Spanish flu were previously present in contemporary human flu strains and that the flu was of completely avian origin. "What makes a virus able to go from an avian reservoir to humans?" Mount Sanai's Garcia-Sastre asked. "That's important. Influenza is mainly a virus of birds. There are many different strains in birds and only a few affect humans. Pandemics occur when one of these jumps into the human population and can affect people by propagating from person to person." Deadly Virus May Save Lives CDC officials are taking extreme care to safeguard the re-created 1918 virus, though it would not likely lead to a major pandemic if the strain spread among the general population. Tests have shown that mice that had been injected with current flu vaccines were protected from the 1918 strain. "We know that all documented pandemic episodes have involved the emergence of a completely new strain," Garcia-Sastre said. "That happened in 1918, 1957, and in 1968." "There is also evidence that people who were 40 years or older in 1918 were spared," he added. "One hypothesis to explain that is that persons 40 years old or older were exposed to an H1 virus before and had some immunity." Now, decades after its outbreak, the 1918 virus may be a weapon rather than an opponent. "I think we've been able to unmask the 1918 virus, and it's revealing to us some of the secrets that will help us prepare for the next pandemic," said Julie Gerberding, Director of the CDC. links Related articles on Global issues: bird flu issues, polices, impact |
| News articles are reproduced for non-profit educational purposes. | |
website©ria tan 2003 www.wildsingapore.com |