A Vaccine for Humans Clears a Hurdle as Bird Flu Expands
By LAWRENCE K. ALTMAN
New York Times
Avian influenza is still spreading in birds in Asia despite the slaughter of millions of chickens and other poultry, the Food and Agriculture Organization of the United Nations said Wednesday.
The United States also announced a ban yesterday on importing birds and bird products from eight Asian countries where there have been outbreaks of the avian influenza.
Meanwhile, scientists have passed the first major hurdle in the complex process of developing an experimental bird flu vaccine for humans in case it is needed, an official of the World Health Organization said. The scientists are also working to develop a safer and easier test to detect the A(H5N1) strain of avian influenza now spreading across Asia, a mutation of the strain that caused outbreaks in Hong Kong in 1997 and 2003.
The steps are being taken as a precautionary measure because of fears that A(H5N1) might swap genes with a human strain to create a new one that could cause a worldwide epidemic, the organization said. The chance of that occurring is considered low.
So far this season in Thailand and Vietnam, the organization said, 17 people have been infected with the A(H5N1) strain; 13 died. According to the organization, 9 of the 13 Vietnamese cases were fatal, as were all four Thai cases, including that of a Thai boy, 6, whose infection had been previously confirmed. The organization reported his death yesterday.
With the possible exception of two cases in Vietnam, there has been no person-to-person transmission of the A(H5N1) strain.
To develop the vaccine and diagnostic test, three laboratories that are part of the World Health Organization's influenza network are using a new method known as reverse genetics. They are at the Centers for Disease Control and Prevention in Atlanta, St. Jude Children's Research Hospital in Memphis and the National Institute for Biological Standards and Control in London.
The aim is to develop a seed virus that the world organization could deliver within two months at no cost to drug companies that would make the human vaccine.
"Things are evolving according to schedule," said Dr. Klaus Stöhr, leader of the United Nations agency's influenza program.
The technique involves substituting harmless influenza genes for the ones that make the strain lethal to birds. In a conference call on Tuesday, two of the laboratories said that they had completed the first step in the reverse genetics technique and expected to begin testing the resulting virus in chickens and ferrets by next week, Dr. Stöhr said in a telephone interview.
The scientists must make sure that the manufactured virus is harmless to chickens because it must be grown in live eggs. Scientists must also make sure that the genes in the virus do not change during the steps leading up to vaccine production.