An 11-year-old Indonesian boy has died of the virulent H5N1 strain of bird flu, raising the national death toll from the disease to 53, the director of the hospital where the patient was being treated said Sunday.

The boy, who wasn't named by officials, was admitted to the Sulianti Saroso Hospital for Infectious Diseases on Thursday and died Saturday night, said Director Dr. Santoso Suroso.

He was believed to have become infected by dead chickens near his home in south Jakarta, Suroso said.

Almost all of the fatal human cases have been linked to contact with chickens or their droppings.

But the World Health Organization said the virus passed among humans in one large cluster of infections in a single family on Sumatra Island earlier this year.

Indonesia has been criticized for failing to aggressively attack the virus in poultry, either by mass slaughters or vaccination. It has said it lacks the resources to compensate farmers for slaughtered birds.

As of Oct. 11, the H5N1 strain of bird flu had killed at least 148 people worldwide out of 253 cases since it started ravaging poultry stocks in Asia three years ago, according to WHO.