NEW DELHI: Outbreaks of H5N1 bird flu in India’s eastern state of West Bengal, which shares a long border with Bangladesh, have not yet been contained, a senior health official in India said on Wednesday.

“West Bengal is an area of concern because we have had outbreaks with some regularity, it is not fully under control yet,” federal Health Secretary Naresh Dayal said in an interview.

Unlike outbreaks in commercial poultry farms in central Maharashtra state in 2006 and eastern Manipur in 2007, which were more easily reined in, outbreaks in West Bengal involved backyard poultry and these were much harder to control, he said.

“They have not been able to completely depopulate (the infected areas) of birds,” Dayal said, without giving details.

West Bengal has culled nearly four million birds in 14 of its 19 districts since the virus surfaced there early this year, but the virus has proved to be hardier than thought.

Tripura, another Indian state which also borders Bangladesh, reported a H5N1 outbreak in poultry in early April, but Dayal said the virus was detected in only one duck sample while samples from chickens were negative.

In Bangladesh, the virus has spread through 47 of its 64 districts since March 2007 and forced the killing of more than 1.5 million birds but authorities have still been unable to control the virus.

READY TO HELP: While Dayal declined to speculate if the virus might have been reintroduced to India from Bangladesh early this year, he said India was ready to help with sample testing, anti-virals and surveillance training.

“We would be very happy to have regional cooperation. That is an infection that can spread very fast across boundaries,” he said.

Despite surging temperatures in Asia, the H5N1 virus has re-emerged in recent weeks, with outbreaks in poultry seen in South Korea and even a village in the far east of Russia.

The disease has killed two Egyptians so far this month, and two youths in Indonesia, where the virus is endemic, late in March.

The timing is not lost on experts, who believe the virus has adapted to hotter climates. Until a few years ago, it was mainly active, and caused trouble, in the cooler months of October to March.

“It has adapted to hotter climates. Look at Indonesia and the southern parts of Vietnam, they are hot all year round but the virus has become endemic in these places,” said Hong Kong-based microbiologist Guan Yi, a leading expert on the virus.Apart from temperature, other factors sustaining the virus were animal density and humidity, Guan said.

“If the bird population is very high and dense, then the virus can pass from bird to bird, and the weather becomes less important,” Guan told Reuters by telephone.—Reuters