JAKARTA (AFP) - Confirmation of the 100th human bird flu death in Indonesia shows the virus is out of control in the country most ravaged by outbreaks of the disease, experts said Tuesday.

Indonesia´s health ministry on Monday confirmed the death of Virda Sari, a 23-year-old woman from eastern Jakarta who died in hospital early Sunday morning.

Her death brought Indonesia´s death toll to the symbolic milestone, highlighting the deadly nature of a virus that has infected a confirmed 124 people in the country, according to the ministry.

More than half of all bird flu deaths worldwide since 2005 have occurred in Indonesia, World Health Organisation figures show. More than twice as many Indonesians have died of the disease than in Vietnam, which with 48 deaths is the second most affected country.

"The virus is uncontrollable in Indonesia ... it means that viral contamination of the environment is quite high," said Ngurah Mahardika, a virologist at Udayana University on the resort island of Bali, which recorded its first two human deaths from the disease last year.

"The reason is that the virus is not under control in animals right now," he said.

The H5N1 virus is mostly spread to humans through contact with infected poultry, but scientists fear it could mutate into a form easily transmittable between humans. The resulting pandemic could kill millions.

Avian influenza has been particularly prevalent in areas surrounding Jakarta, Mahardika said, with the satellite city of Tangerang in neighbouring Banten province of particular concern with its large population living close to poultry.

Tangerang has seen eight confirmed human infections since October last year, all of them fatal.

A quarter of Indonesia´s bird flu deaths have occurred in Jakarta, with another 45 percent striking in Banten and the nearby province of West Java, according to health ministry figures.

Both provinces abut the massive capital and receive the overflow of its urban sprawl.

A lack of coordination between government agencies means authorities are not sharing disease samples, raising the possibility of missing detecting strains of the virus that have adapted to humans, Mahardika said.

"The people working in this field never come to the table to talk about it and analyse it together," he said.

Devolution of power over the last 10 years since the fall of authoritarian president Suharto has also hindered coordination efforts, Australian National University Indonesia expert James Fox said.

"You have an area that will try to contain the bird flu epidemic, but there´s no guarantee the neighbouring area will do the same. So (bird flu) will always just come back," Fox said.

Unlike other Asian nations which have managed to contain the bird flu virus, Indonesia´s gross oversight was to not begin exterminating poultry three or four years ago when the disease first began spreading, he said.

"Most of the other nations decided they would not vaccinate, they would exterminate. The problem is on a veterinary level, (Indonesian authorities) were in denial," Fox said.

"(Exterminating poultry) is not possible anymore, you can only do that when there´s a small outbreak, when it first begins. It is now endemic," Fox said.

Muchtar Ihsan, the doctor at the head of the avian influenza team at Jakarta´s Persahabatan hospital -- one of two bird flu referral hospitals in the capital -- said Indonesia´s long practice of families living close to their poultry has proved hard to break.

"This is the habit of the people since hundreds of years ago, it´s hard to convince people that it´s dangerous," he said.