A Turkish teenager whose brother died of bird flu also succumbed to the disease Thursday, a Turkish doctor said. A senior World Health Organization official said tests pointed to a strain scientists fear could trigger a global human epidemic. If confirmed, the brother and sister would be the first human cases of the H5N1 strain in Turkey, signaling that the virus is moving westward from the far eastern corner of Asia. Guenael Rodier, a special adviser on communicable diseases at WHO's European headquarters in Copenhagen, Denmark, said samples from the brother had been tested by two laboratories in Turkey and "it turned out to be positive (for H5N1), and because it's so specific it's unlikely we're dealing with false positives. There's no reason to believe it's wrong." Specimens are now on their way to centers in Britain, where the initial test results will be checked, Rodier told The Associated Press in a telephone interview. Fatma Kocyigit, 15, died in a hospital in the eastern city of Van, four days after the death of her 14-year-old brother, Mehmet Ali Kocyigit, the Anatolia new agency reported, citing Ahmet Faik Oner, the doctor who treated the siblings. Their 11-year-old sister, Hulya, was hospitalized with suspected bird flu. The siblings from the eastern town of Dogubeyazit, close to Iranian border, were admitted to the hospital last week after developing high fevers, coughing and bleeding in their throats. Eight other people with similar symptoms were being treated at the hospital, said Huseyin Avni Sahin, head physician at the hospital. Sahin told private NTV television that some other patients were hospitalized in the eastern city of Erzurum because his hospital was not capable of handling more cases.