An outbreak of avian flu in Mongolia seems to have died out quickly on its own, wildlife experts said Thursday, raising questions about how easily migrating birds will spread the virus.
They said only about 100 birds seemed to have succumbed to the virus in an outbreak at Erkhel Lake, near where the borders of Russia, China, Kazakhstan and Mongolia meet.
At least some of the birds that died carried an H5 avian influenza virus, said Wildlife Conservation Society veterinarian William Karesh.
But he cautioned that it has not been confirmed as the frightening H5N1 virus that is affecting flocks in China, Japan, Vietnam, Thailand, Russia and perhaps also Kazakhstan.
“We found it was H5 influenza,” Karesh told Reuters in a telephone interview.
But only about 100 of the 6,500 birds on the lake, representing 55 different species, had died, he added.
“So we are talking about a tiny percentage of mortality,” he said.
Avian influenza has decimated flocks of chickens in an outbreak that started in 2003, and has killed about 50 people. Experts fear it will eventually acquire the ability to spread easily from person to person and cause a global pandemic of exceptionally deadly influenza.
No one is sure how it is spreading, but migrating birds are a prime suspect. Officials fear migrating birds could export the virus to Western Europe, Africa and the Middle East over coming months.
In Russia it has spread across Siberia to the Ural mountains, the geographic divide between Asia and Europe.
Karesh led a team to Mongolia because of its position on the borders of countries involved.
While there, they heard birds were dying at a small lake called Lake Erkhel so they went there.
“Sure enough, birds were dying,” Karesh said. They sampled some of the dead swans, geese and gulls, and also collected samples from healthy birds.
“In this situation it had a very low impact,” Karesh said.
“It makes the disease self-limiting in wild birds.”
Karesh said he will wait for full results of tests being done by U.S. Department of Agriculture labs in Georgia on the samples taken from healthy birds at the lake, as well as tests to confirm the dead birds carried H5N1 and not another H5 virus.
Experts say the key to spreading influenza would be healthy birds that are not sickened by the virus. If the virus kills an animal quickly, it is less likely to spread it.
“Currently, all evidence points to domestic ducks as the ones who can shed it and transmit it and not get sick,” Karesh said.
But the jury is out on wild birds as being major spreaders of the virus, Karesh said. “If we have lots of wild birds shedding it and they look healthy, that would be pretty good evidence that they are,” he said.
“The key to this is better security on poultry production,” he added. If farmer use fencing, roofing and clean water to separate ducks and chickens from wild birds, that will likely limit the spread of the disease, he said.
The Dutch Agriculture Ministry has done that, saying Tuesday it would make farmers keep all poultry indoors to prevent contact with migrating birds. German officials are considering similar measures.
But Thursday Russian media reported that some Russian regions have opened the hunting season early for wild birds to try to limit the spread.