Scientists find why bird flu doesn't spread easily Virus infects deep in respiratory tract; not passed by coughing, sneezing
Updated: 11:33 a.m. ET March 24, 2006
NEW YORK - Scientists say they’ve found a reason bird flu isn’t spreading easily from person to person: The virus concentrates itself too deep in the respiratory tract to be spewed out by coughing and sneezing.
But the virus could change that behavior by genetic mutation, taking a step toward unleashing a worldwide outbreak of lethal flu.
Experts said the new finding doesn’t indicate how likely such a pandemic is. The virus may also need other mutations to take off in the human population, they said. Still, the work suggests a particular sign to watch for in new virus samples to help gauge the danger to humans.
The work, reported in Thursday’s issue of the journal Nature, comes from University of Wisconsin-Madison virologist Yoshihiro Kawaoka with colleagues in Japan. Similar results, from the Erasmus Medical Center in Rotterdam, the Netherlands, will be published online Thursday by the journal Science.
More than 180 people are known to have been infected with the bird flu virus H5N1. Virtually all are believed to have caught it from infected poultry. But scientists have long warned that the virus, which is prone to mutation, could transform itself into a version that spreads easily from person to person. That germ could touch off a pandemic.
Ordinary flu viruses spread when an infected person coughs or sneezes, blasting out tiny droplets carrying the germ to others. For that to happen, the virus has to be perched in the right places to be ejected by a cough or sneeze. The new work suggests H5N1, by contrast, infects humans too low in the respiratory tract for that to occur.
Both research teams used human tissue removed from various parts of the respiratory tract — the region from the nose to the lung — to study where virus infection occurs.
Scientists already knew that bird flu viruses use a specific kind of docking site to enter cells they infect, while human flu viruses use a different one. Kawaoka’s group found the bird virus docking site appears mostly on lung cells, while being rare on cells found in higher areas like the nose and windpipe. Those higher areas were dominated instead by the human-type docking site.
Kawaoka said that for H5N1 to become a pandemic virus, it would have to mutate in a way that lets it attach to the same docking site human viruses use. Other mutations would be needed as well, he said in a statement.
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Robert M. Krug of the University of Texas at Austin called Kawaoka’s work an important observation, and said that if H5N1 begins to use the human virus docking site “we’ve got a lot to worry about.” It’s not clear whether that would be enough to produce a pandemic germ, he said.
James Paulson of the Scripps Research Institute in La Jolla, Calif., stressed that other viral factors may be important in human-to-human transmission. But he said that once the virus has a foothold in a person, regardless of where it is in the respiratory tract, it may mutate to gain the abilities it needs to start spreading among people.
Schools urged to prepare for bird flu How will students be taught if classes are shut down during pandemic?
Updated: 10:25 a.m. ET March 22, 2006
WASHINGTON - The nation’s schools, recognized incubators of respiratory diseases among children, are being told to plan for the possibility of an outbreak of bird flu.
Federal health leaders say it is not alarmist or premature for schools to make preparations, such as finding ways to teach kids even if they’ve all been sent home.
School boards and superintendents have gotten used to emergency planning for student violence, terrorism or severe weather. Pandemic preparation, though, is a new one.
They have a lot to think over, top government officials said Tuesday.
Who coordinates decisions on closing schools or quarantining kids? If classes shut down for weeks, how will a district keep kids from falling behind? Who will keep the payroll running, or ease the fear of parents, or provide food to children who count on school meals?
“Those are the kinds of issues that I don’t think people have spent a lot of time talking about yet,” said Stephen Bounds, director of legal and policy services for the Maryland Association of School Boards.
“But if New Orleans and Katrina taught us nothing else, it taught us you need to be thinking about things ahead of time — and preparing for the worst,” Bounds said.
As the numbers of birds and humans abroad infected with a deadly form of the H5N1 virus rises, U.S. hospitals also need to get ready now, a federal bird flu expert said Tuesday at a meeting of epidemiologists in Chicago.
“It’s extremely important to investigate every H5N1 case,” said Dr. Timothy Uyeki of the federal Centers for Disease Control and Prevention.
Many U.S. hospitals are still in the planning stage for a pandemic. But the University of Chicago Hospitals are a bit further along. Patients who arrive there with flu symptoms are routinely asked about recent travel to places where bird flu is rampant.
The deadly H5N1 strain of bird flu remains primarily a contagious bird disease. Typically spread from direct contact with contaminated birds, it has infected more than 170 people and killed roughly 100. None of those cases occurred in the United States, but officials say bird flu is likely to arrive this year in birds.
As outbreaks have hit Africa, Asia and Europe, officials have launched campaigns to educate the public. To help stop the spread of the disease, farmers have killed tens of millions of chickens and turkeys.
Experts fear the virus could change into a form that passes easily among people.
Common sense advice In North Carolina on Tuesday, Education Secretary Margaret Spellings joined Health and Human Services Secretary Mike Leavitt to encourage schools to prepare. Spellings said schools must be aware that they may have to close their buildings — or that their schools may need to be used as makeshift hospitals, quarantine sites or vaccination centers.
The government has created checklists on preparation and response steps, specialized for preschools, grade schools, high schools and colleges. The dominant theme is the need for coordination among local, state and federal officials.
Some of the advice is common sense, like urging students to wash their hands and cover their mouths when they cough or sneeze to keep infection from spreading. Other steps would take schools considerable time to figure out, such as legal and communication issues.
“I don’t think that the issue of bird flu has resonated yet,” said Reg Weaver, president of the National Education Association, which represents many of the country’s teachers.
Weaver praised the federal government for providing guidance that can be plugged into a school district’s crisis plan. But the sudden urgency on bird flu, he said, should not steal attention from the daily struggles schools face, like trying to keep their classrooms safe.
Children age 5 to 18 tend to be the biggest spreaders of flu viruses in the community, experts say. Schools may be ordered to close to prevent spreading the disease.
In Massachusetts, school administrators are considering using an automated phone bank to announce homework assignments and update parents. Another plan would use the Internet for communication between students and their teachers.
But those plans are limited, and many places have had budget cuts in technology, said Tom Scott, executive director of the Massachusetts Association of School Superintendents. “I don’t think we’re anywhere near having a systemic way of approaching this,” he said.
Any school closing may not be for only a day or two. A shutdown would probably have to last a month or longer to be effective, said flu specialist Ira Longini, a faculty member at the Fred Hutchinson Cancer Research Center and a professor at the University of Washington in Seattle.
“The school itself plays a big role,” said Longini. “It’s just a massive mixing ground for respiratory illness.”
At the college level, the American Council on Education, a higher education umbrella group, has alerted thousands of college presidents about the need to prepare for bird flu.
Federal health leaders have advised each college to establish a pandemic response team and plan for outbreak scenarios that could close or quarantine their campuses.
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