A report by BBC News has confirmed the first case of human-to-human transmission of bird flu in Pakistan.
Pakistan's north-west and southern regions were hit by bird flu last year. Thousands of birds were culled to control the spread of the disease.
Tests carried out by the World Health Organisation (WHO) have now shown that bird flu killed some members of a family in north-west Pakistan late last year.
This is the first confirmation of people dying from bird flu in the country, with the samples collected from the family in Peshawar testing positive.
According to Dr Mukhtiar Zaman Afridi, head of the isolation ward for avian flu patients at Khyber Teaching Hospital in Peshawar, a poultry worker in Peshawar apparently passed the disease on to members of his family.
"The worker, whose name is being withheld on the request of the WHO, was brought to the hospital with avian flu symptoms on 29 October 2007," he said.
Though this worker has fully recovered since then, on 12 November, his elder brother was brought in with similar symptoms. He died a week later.
On 21 November, two more brothers of the same worker came down with bird flu.
"One of them died on 28 November, while the other has recovered," said Dr Afridi.
Apart from the poultry worker, none of the others was found to have had any direct contact with sick or dead poultry.
Genetic sequencing tests performed by WHO laboratories in Egypt and the US on samples collected from three of the four brothers established human-to-human transmission.
Serum taken from all three were found to have been infected by the H5N1 avian influenza virus.
Though a WHO report said that the tests suggest "limited human-to-human transmission," it adds, however, that this "outbreak did not extend into the community, and appropriate steps were taken to reduce future risks of human infections."