Officials in India's West Bengal state, which borders Bangladesh, have been struggling to contain that country's worst-ever outbreak of the virulent H5N1 bird flu virus.
The global spread of highly pathogenic H5N1 in birds is considered a significant pandemic threat. While other H5N1 strains are known, they are significantly different from a current, highly pathogenic H5N1 strain on a genetic level, making the global spread of this new strain unprecedented. The H5N1 strain is a Fast-mutating, highly pathogenic aviab influenza virus (HPAI) found in multiple bird species. It is both epizootic (an epidemic in non-humans) and panzootic (a disease affecting animals of many species especially over a wide area).
Several hundred chickens died at the poultry farm in Dinajpur district, 270 kilometers north of Dhaka, and laboratory tests confirmed that the H5N1 virus was responsible.
More than 27,000 chickens and ducks were killed and more than 60,000 eggs were destroyed on Thursday and Friday in an attempt to halt the spread of the virus, the agency said.
On Thursday, the government warned the Department of Livestock that more precautions were needed to prevent the disease from spreading.
Any widespread outbreak can be disastrous for Bangladesh because of its dense population and poorly equipped public health care system.
Bird flu has been confirmed in at least 30 of Bangladesh's 64 districts and has struck more than 97 farms since it was first detected in February last year. More than 350,000 birds have been slaughtered.
No cases of human infection have been reported.
Bangladesh recently tightened controls along its porous border with India, with authorities ordering officials to block all imports of poultry and eggs from that country.
In India, more than 129,000 poultry have died from bird flu in West Bengal state in recent weeks and nearly 2.5 million at-risk birds have been slaughtered, according to Animal Resource Development Minister Anisur Rahaman. Officials fear the disease could reach crowded Calcutta and its 14 million people.
Infected birds pass on H5N1 through their saliva, nasal secretions, and faeces. Other birds may pick up the virus through direct contact with these excretions or when they have contact with surfaces contaminated with this material. Because migratory birds are among the carriers of the H5N1 virus it may spread to all parts of the world. Past outbreaks of avian flu have often originated in crowded conditions in southeast and east Asia, where humans, pigs, and poultry live in close quarters. In these conditions a virus is more likely to mutate into a form that more easily infects humans. A few isolated cases of suspected human to human transmission exist, with the latest such case in June 2006 (among members of a family in Sumatra). No pandemic strain of H5N1 has yet been found.
The virus remains hard for people to catch, but experts worry it could mutate into a form that passes easily among people, igniting a flu pandemic. Most human cases have been traced to contact with infected birds. H5N1 has killed at least 224 people worldwide, according to the World Health Organization.