Professor seeks signs of avian flu

Scientists are tracking wild birds for to see if the strain reaches North America.
CLEVELAND (AP) -- A veterinary professor at Ohio State University is part of a national effort to identify and track the avian flu virus that many fear will fuel a pandemic.
Richard Slemons spends days wading through knee-high marsh in a Lake Erie preserve teeming with wild birds. One day last month, Slemons' van contained fecal samples from about 130 ducks.
While there has been avian flu in the United States, it has not been the H5N1 strain that has spread through poultry farms in southeast Asia and into eastern Europe. In two years, it has infected 117 people, all in Asia. More than 60 have died.
Slemons and other U.S. scientists are tracking wild birds -- a common reservoir for influenza viruses -- so they know when strains are on the move.
"It could become the next pandemic," said Slemons. "But you cannot predict what a flu virus will do. The more we understand about flu viruses, the more complicated they become."
Public health experts do not know if the H5N1 strain will spread to birds and other species in North America, but they aren't taking chances.
Animal scientists are examining birds along North America's five key avian routes, including a waterfowl route through southern Ontario and western Lake Erie before veering southwest across Ohio and Indiana to the Mississippi River.
Discovery
Ohio State is involved because of Slemons' reputation. Thirty years ago he discovered that migratory ducks infected with avian influenza harbored the germ in their intestinal tracks. Slemons pointed scientists toward the natural reservoir of type A influenza genes that, over time, get passed on to humans, pigs and other mammals through what is called genetic reassortment.
But how wild birds manage to accommodate the avian strains of a mutating virus remains a mystery. "Every year we see different subtypes of flu, but sometimes you don't see a subtype for two or three years and all of a sudden it reappears," Slemons said.
Most avian strains grow in the intestines of wild birds and are excreted within a week to 10 days. The droppings pose a danger to other birds.
"Birds typically have no symptoms," said Dr. Hon Ip, a virologist at the National Wildlife Health Center in Madison, Wis. "But H5N1 is different. It replicates more efficiently and causes systemic infection. All the bird's major organs, including the lungs, are infected. It's very unusual."
No signs
So far, scientists have no proof the H5N1 virus has come into the United States via breeding grounds shared by the North American and Asian flyways.
"Hopefully, we can detect it [early] if it does happen," said Dr. David Swayne, an animal virologist at the U.S. Department of Agriculture's Southeast Poultry Research Laboratory in Georgia. "H5N1 in Asia has changed. In 1998, it was not infecting wild ducks. But as recently as 2002, the virus has shown its ability to infect some wild birds, including some species of ducks. Why? It could be the virus is changing its pattern."