A 27-year-old woman was killed by bird flu — Indonesia's third death from the virus in as many days — bringing the nation's toll to 55, the World Health Organization said Tuesday.

The woman from Central Java province died Friday, five days after she developed symptoms of the disease and one day after she was hospitalized, the WHO said in a statement posted on its Web site.

"The source of her exposure is currently under investigation," it said.

According to WHO, of the 72 cases confirmed to date in Indonesia, 55 have been fatal.

An 11-year-old boy succumbed to the disease in a Jakarta hospital on Saturday and a 67-year-old woman died Sunday in the West Java town of Bandung, Indonesian health officials announced earlier this week.

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The H5N1 virus has killed at least 151 people worldwide since it began ravaging Asian poultry stocks in late 2003, according to WHO.

Most of those killed have been infected by domestic fowl, but WHO fears the virus could mutate into a form that easily spreads among humans, sparking a pandemic with the potential to kill millions.

Indonesia, the world's fourth most populous country and home to millions of backyard chickens, is considered a hot spot for that to happen.

The government has been criticized for failing to aggressively deal with the virus in poultry stocks, either by mass slaughters or vaccination.

CountryWatch:Indonesia