Outbreaks Show Bird Flu Virus Is Changing

But its potential for human-to-human spread remains unclear.

By E.J. Mundell
HealthDay Reporter
Wednesday, November 22, 2006; 12:00 AM

Copyright © 2006 ScoutNews, LLC. All rights reserved.

WEDNESDAY, Nov. 22 (HealthDay News) -- Detailed data on clustered human cases of avian flu have experts agreeing that the H5N1 virus is evolving -- but in what direction?

"The virus is always changing, and the mutations that make it more compatible with human transmission may occur at any time," warn Drs. Robert Webster and Elena Govorkova, both virologists at St Jude's Children's Research Hospital in Memphis, Tenn.

Their commentary accompanies reports from Indonesia and Turkey, both published in the Nov. 23 issue of the New England Journal of Medicine.

However, another expert believes that, so far, H5N1 has given no indication it is mutating toward human-to-human transmission.

"It's far from a certainty," said Dr. Marc Siegel, a clinical associate professor of medicine at New York University School of Medicine, and author of Bird Flu: Everything You Need to Know About the Next Pandemic. "The virus could move closer to human-to-human transmission, and it could move farther away. I don't think that you can conclude from these articles in the NEJM that the thing is becoming easier to transmit."

The two studies' most basic data is not new. They focus on three clusters of H5N1 infection in Indonesia in mid-to-late 2005, involving four deaths, and an eight-patient cluster treated in the first weeks of 2006 at a hospital in far-eastern Turkey. Four of the Turkish patients died.

Details published in the journal do point to some intriguing trends, however.

As noted in other cases, almost all infections were linked to close handling of domestic fowl. More troubling was the fact that the Turkish group, led by Dr. Ahmet Oner, of Yuzuncu Yil University, in Van, found it very difficult to diagnose H5N1 in humans at its earliest stages.

Two standard tests turned up negative for the virus, and only a high-tech "polymerase-chain-reaction assay" confirmed H5N1 as the culprit. Infection also "causes a wide spectrum of illnesses in humans," the study authors wrote, with symptoms varying widely among patients.