Two more Indonesians have been confirmed as infected with the H5N1 bird flu virus, a health official said on Monday, citing results from a World Health Organization-recognized laboratory in Hong Kong.

The two confirmations will bring the H5N1 death toll in Indonesia to 36, and its total number of H5N1 infections to 49.

One of them was an 18-year-old male from Bandung on Java island who had tested negative earlier in Hong Kong. The latest result classified him as a H5N1 case, said I Nyoman Kandun, director-general of communicable disease control.

He was the brother of a 10-year-old girl, who tested positive for H5N1 by the Hong Kong laboratory last week. Both died last Tuesday.

Local health authorities believe sick chickens to be the source of the siblings’ infection as poultry started dying in the village where they lived a few days before they fell ill, Kandun said.

The Bandung siblings are considered the seventh family cluster in Indonesia, but their case is not triggering as much concern as another cluster in north Sumatra, where H5N1 killed seven people in a single family.

The brother and sister fell sick at about the same time, and Indonesian experts believe they may have been exposed to, and infected by, the same source.

Experts say limited human-to-human transmission of the virus may have occurred in the Sumatran family because several of the members took care of those who fell sick earlier and may have picked up the virus during such close and prolonged contact.

However, genetic analyses of the virus have not found all of the changes or traits that are known to date which will allow the virus to spread efficiently among people - a necessary precursor to the start of a pandemic.

Kandun said a 15-year-old girl from Solok in western Sumatra, who is fighting for her life, also tested positive, according to results from the Hong Kong laboratory.