Fears of a global bird flu pandemic that once dominated headlines have largely vanished in the West, but four years after the virus began ravaging Asian poultry, it continues to quietly spread.
Most global health officials continue to warn that the virus could morph into a disease as threatening to people as it is to chickens. Although a few are now calling the risk "overestimated," recent developments raise new concerns:
- This week marked the 100th death in Indonesia since the virus was first reported in humans there in 2005.
- India is battling its worst-ever poultry outbreak. No human cases have been reported, but experts are scrambling to keep the disease from reaching crowded Calcutta and its 14 million people.
- Pakistan and Myanmar both reported their first human infections in December. That brings to 14 the number of countries where the virus has jumped from poultry to people.
The H5N1 bird flu virus still has killed relatively few people since it began destroying Asian chickens and ducks in late 2003. More than 220 people have died, nearly all from close contact with infected birds. About 60 percent who catch the virus die.
Is risk to humans overestimated?
The most recent death in Vietnam — one of the countries most successful at quashing the virus — offers a typical illustration of how people get infected. A man died after butchering and cooking geese and chickens that had died at his backyard farm. Tests showed they had the H5N1 virus. The victim was Vietnam's 48th since 2003.
Still, the virus' inability to more easily infect and spread among people has led some experts to distance themselves from the idea it could someday gain the power to kill millions like the world's worst flu pandemic nearly 100 years ago.
A few weeks ago, Bernard Vallat, director general of the Paris-based animal health organization, known as OIE, said "the risk was overestimated" and fear of an imminent pandemic was "just nonscientific supposition."
Officials with the World Health Organization maintain that the threat has not lessened, but acknowledge increasing bird flu fatigue.
"It's not an issue which is always going to remain on the front pages of newspapers," said Gregory Hartl, WHO spokesman in Geneva. "But that doesn't change the public health assessment of the situation."
Bird flu has already caused a pandemic in poultry. Hundreds of millions of birds in more than 60 countries — from Vietnam and Egypt to Britain and Nigeria — have died or been slaughtered to halt its spread.
"A normal pattern in many countries has been that where there are widespread poultry outbreaks, you do get human cases," Hartl said. "The virus is out there and is still a threat."
Spread of disease hard to control
Indonesia remains a constant concern. Health experts are unsure why it continues to post cases year-round when most other nations typically only experience sporadic bumps.
It may be because people wait too long to seek treatment. Or it could be connected to the type of virus circulating there, which differs genetically from H5N1 elsewhere. Indonesia's sheer volume of poultry combined with the amount of disease present in flocks may also be playing a major role.
The ongoing poultry outbreaks in India illustrate how hard it is to control. Nearly 2.5 million birds have been slaughtered since mid-January, and farmers angry about low compensation for their chickens have been hiding or smuggling birds out of the area, said Anisur Rahaman, animal husbandry minister in West Bengal state.
Initially, there were reports of dead birds being tossed in ponds or buried in shallow pits. Officials were forced to conduct nighttime raids to round up backyard poultry under the cover of darkness, he added.
A number of other countries, including Thailand and Bangladesh, have also recently detected poultry outbreaks during the winter months when the virus typically flares.
Experts believe the spread is largely related to the trade of birds and their products, including cross-border smuggling. Wild birds are believed to play a role, but a recent WHO review published in the New England Journal of Medicine said the risk of the H5N1 virus reaching North America through migrating birds remains low.
Next week a recurring annual challenge faces health officials: the Lunar New Year, a festival that rivals Christmas in the West. Throngs of Asians will be traveling, carrying their chickens and ducks with them.