Snowy Owl
Retired in 2010, In Memoriam
1 bird flu strain dominant, spreading
Danger to humans no higher, study says
http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/10/31/MNG1GM32SQ1.DTL
All thanks to The Los Angeles Times & San Francisco Chronicles for their Public Health Services
Danger to humans no higher, study says
http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/10/31/MNG1GM32SQ1.DTL
All thanks to The Los Angeles Times & San Francisco Chronicles for their Public Health Services
Karen Kaplan, Los Angeles Times Tuesday, October 31, 2006
A strain of H5N1 avian influenza identified last year has become dominant in southern China and is the source of a new wave of bird flu in Southeast Asia, scientists reported Tuesday.
The so-called Fujian-like strain has infected poultry in Hong Kong, Laos, Malaysia and Thailand and sickened people in China and Thailand.
While five people in China have been infected by the strain, the virus does not appear to have improved its ability to spread among humans, according to the study published in the Proceedings of the National Academy of Sciences.
"There's no evidence in this paper of additional human-to-human transmission, which is the real bottom line we're all worried about," said Robert Webster, a virologist at St. Jude Children's Research Hospital in Memphis and coauthor of the study. "But so long as the virus is out there in these numbers, it's going to be a continuing pandemic threat."
The researchers also said the vaccine administered to birds in China is ineffective against the strain and might have facilitated its proliferation among the country's 15 billion chickens, geese and ducks by eliminating weaker flu strains.
"With China immunizing all of these birds, they're basically driving the evolution (of H5N1)," said Henry Niman, president of a virus and vaccine research company in Pittsburgh called Recombinomics Inc. He was not involved with the study.
The report, based on China's flu surveillance program, found that H5N1 became more prevalent between July 2005 and June 2006 compared with the previous year.
The researchers tested 53,220 birds in live poultry markets and found that 2.4 percent tested positive for any strain of H5N1, up from 0.9 percent a year earlier.
Researchers found that ducks and geese were the most common carriers, and that they were susceptible to bird flu year-round.
Chickens tend to succumb only in the winter, but the researchers discovered cases in 11 of the 12 months of their study, up from four of 12 months the previous year.
The Fujian-like strain, named after the coastal Chinese province where it was first identified, has risen steadily in prevalence over the past year, accounting for 103 of the 108 samples tested between April and June this year, according to the report.
The emergence of a dominant strain does offer some advantages.
"In the short term, it's easier to control a single dominant lineage than a number of smaller ones," said Richard Webby, an influenza researcher at St. Jude's Research Hospital who was not connected with the study.
But a dominant strain is also more likely to spread widely. That has happened twice since H5N1 was first identified in China in 1996.
The first wave of outbreaks was limited to Asia, but the second wave traveled from western China's Qinghai Lake in 2005 to Europe and Africa -- and continues to spread.
Although H5N1 is widespread in birds, no strain that has emerged so far is adept at crossing the species boundary to infect humans. Since 2003, 256 people have been infected with H5N1, resulting in 151 deaths, according to the World Health Organization.
Even more rare are cases of the virus jumping directly from person to person -- a necessary ingredient for a pandemic.
But the chances of such a strain emerging increase with each new infection. The worst-case scenario is that a person would be infected simultaneously with bird flu and a regular human flu, giving the two viruses a chance to reshuffle their genetic elements to create a deadly strain that spreads easily from person to person.
Dr. David Nabarro, who coordinates the United Nations' efforts against human and avian influenza, said the new data are a reminder that H5N1 is constantly evolving.
"I don't think it's a sign that we're getting any closer to pandemic flu," Nabarro said. "Frankly, I don't know how we're going to know when pandemic flu gets close. We're just going to get hit by it."
A strain of H5N1 avian influenza identified last year has become dominant in southern China and is the source of a new wave of bird flu in Southeast Asia, scientists reported Tuesday.
The so-called Fujian-like strain has infected poultry in Hong Kong, Laos, Malaysia and Thailand and sickened people in China and Thailand.
While five people in China have been infected by the strain, the virus does not appear to have improved its ability to spread among humans, according to the study published in the Proceedings of the National Academy of Sciences.
"There's no evidence in this paper of additional human-to-human transmission, which is the real bottom line we're all worried about," said Robert Webster, a virologist at St. Jude Children's Research Hospital in Memphis and coauthor of the study. "But so long as the virus is out there in these numbers, it's going to be a continuing pandemic threat."
The researchers also said the vaccine administered to birds in China is ineffective against the strain and might have facilitated its proliferation among the country's 15 billion chickens, geese and ducks by eliminating weaker flu strains.
"With China immunizing all of these birds, they're basically driving the evolution (of H5N1)," said Henry Niman, president of a virus and vaccine research company in Pittsburgh called Recombinomics Inc. He was not involved with the study.
The report, based on China's flu surveillance program, found that H5N1 became more prevalent between July 2005 and June 2006 compared with the previous year.
The researchers tested 53,220 birds in live poultry markets and found that 2.4 percent tested positive for any strain of H5N1, up from 0.9 percent a year earlier.
Researchers found that ducks and geese were the most common carriers, and that they were susceptible to bird flu year-round.
Chickens tend to succumb only in the winter, but the researchers discovered cases in 11 of the 12 months of their study, up from four of 12 months the previous year.
The Fujian-like strain, named after the coastal Chinese province where it was first identified, has risen steadily in prevalence over the past year, accounting for 103 of the 108 samples tested between April and June this year, according to the report.
The emergence of a dominant strain does offer some advantages.
"In the short term, it's easier to control a single dominant lineage than a number of smaller ones," said Richard Webby, an influenza researcher at St. Jude's Research Hospital who was not connected with the study.
But a dominant strain is also more likely to spread widely. That has happened twice since H5N1 was first identified in China in 1996.
The first wave of outbreaks was limited to Asia, but the second wave traveled from western China's Qinghai Lake in 2005 to Europe and Africa -- and continues to spread.
Although H5N1 is widespread in birds, no strain that has emerged so far is adept at crossing the species boundary to infect humans. Since 2003, 256 people have been infected with H5N1, resulting in 151 deaths, according to the World Health Organization.
Even more rare are cases of the virus jumping directly from person to person -- a necessary ingredient for a pandemic.
But the chances of such a strain emerging increase with each new infection. The worst-case scenario is that a person would be infected simultaneously with bird flu and a regular human flu, giving the two viruses a chance to reshuffle their genetic elements to create a deadly strain that spreads easily from person to person.
Dr. David Nabarro, who coordinates the United Nations' efforts against human and avian influenza, said the new data are a reminder that H5N1 is constantly evolving.
"I don't think it's a sign that we're getting any closer to pandemic flu," Nabarro said. "Frankly, I don't know how we're going to know when pandemic flu gets close. We're just going to get hit by it."
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