Let's Talk Turkey
The greatest worry about the latest bird flu news is not that the H5N1 virus has taken root beyond eastern Asia into multiple provinces of Turkey. No, the real issue is that the deadly H5N1 virus seems to be changing its stripes. What's evident from the Turkish outbreak is that the virus is being more rapidly and efficiently transmitted from birds to humans than has been seen in the past. We don't know why. But preliminary studies of the genetic makeup of samples of the deadly virus last week confirm that the virus is mutating in a way that could make it an even more serious threat to human health.
In October, using aggressive quarantine and culling of birds, Turkey seemed to have quelled an isolated spate of H5N1 virus in chickens in the town of Kiziksa near Istanbul. Things were quiet until mid-December when suddenly and dramatically, in a pattern not seen before, bird flu mushroomed into multiple, nearly simultaneous outbreaks throughout the country. It went from nowhere to seemingly everywhere in a matter of 15 days. Then, on New Year's Eve, came the first of the human infections--four siblings were hospitalized; three of them died. Twelve days later, the number of human cases surged to 18, mostly in children, and all had contact with sick chickens or ducks. That's 18 cases in less than two weeks, when the rest of the world had seen only 143 in three years.
But the new Turkish outbreak comes with yet another twist: Aside from the three children who died, most of the other patients with confirmed infection had mild flu symptoms or none at all. Tayfun Ozcelik, professor of molecular biology and genetics at Bilkent University in Ankara, says that this milder behavior as well as the more efficient transmission raises the specter that the H5N1 virus is evolving in a way reminiscent of the bird flu virus that caused the 1918 pandemic--that is, through a series of slow, incremental mutations that make it gradually adapt to life in humans.
Yes, milder is better for those who get the milder illness, making the disease seem more benign to them. But it's not necessarily a positive development for public health if more people get infected yet the virus remains deadly to a large segment of the population. For the H5N1 bird flu, that susceptible segment is mostly among otherwise healthy children and young adults. The World Health Organization stresses that despite these developments, there is absolutely no evidence so far that healthy people have caught this virus from infected patients, a vital step in conversion of epidemic to pandemic.
Summer home. The unique Turkish situation has raised another issue critical to the spread of this virus. That is whether migrating waterfowl like ducks might explain the peculiar burgeoning of the disease in late December. Wild birds are citizens of the world, crisscrossing the globe each year. Turkey is noteworthy in this regard. It lies within several major flight paths as birds migrate from the cold winters of places like Siberia to warm southern spots like North Africa. According to Thomas Van't Hof, an ornithologist at Wright State University who studies migration patterns of wild birds, Turkey, with its many lush marshes, is a favorite pit stop where wild birds rest, stock up on food and water, and leave their detritus behind. Other birds from Asia winter in Turkey as well.
For the longest time, scientists dismissed the possibility that migrating waterfowl infected domestic animals. To the contrary, wild birds were seen as victims, not vectors, of H5N1. As the theory goes, dead ducks don't fly, and once infected, they don't go very far. But this thinking is changing with evidence that a milder, asymptomatic strain of H5N1 has evolved in some waterfowl that is deadly to chickens. These so-called Trojan ducks, described in the July issue of the Proceedings of the National Academy of Sciences, have made scientists reconsider migrating wild birds as players in H5N1 outbreaks.
Time will sort this all out. Wild birds are slated for more aggressive surveillance and testing for virus as they reassemble in their summer homes this spring in places like Alaska, a well-known international haven for birds that have wintered all over the world.
It's too early to be sure, but Turkey may be a turning point in the evolution of a potential pandemic. In any event, this unusual burst of bird flu in its midst will teach the world some important lessons as we move ahead to contain this threat.
This story appears in the January 23, 2006 print edition of U.S. News & World Report.