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JAKARTA, July 9 (Reuters) - A 6-year-old Indonesian boy died of bird flu at the weekend, bringing the country's death toll from the disease to 81, officials said on Monday.

The boy, from the city of Cilegon in Banten province, suffered from high fever and breathing difficulties before he died of multi-organ failure on Sunday, said Tuty Hendrarwardati, the spokeswoman of Jakarta's bird flu hospital.

The victim's family and neighbours did not have any chickens in their backyard, Hendrarwardati said.

Joko Suyono from the health ministry's bird flu centre said it was not clear how the boy got the infection.

"We are still investigating how he had contracted the virus. So far, we only know that he visited the Bandung zoo," Suyono said.

Bird flu is endemic in bird populations in most parts of Indonesia, where millions of backyard chickens live in close proximity with humans.

Contact with sick fowl is the most common way for humans to contract the H5N1 virus.

Experts fear if an easy means of transmission from human to human develops, there might be a pandemic affecting millions.

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