WHO says bird flu cluster shows no evidence of virus mutating

The World Health Organisation (WHO) has confirmed that a 32-year-old Indonesian man from Sumatra died on May 22 from the H5N1 strain of bird flu.

The man is the seventh member of a family cluster in North Sumatra to become infected with the H5N1 virus and the sixth to die.

The cluster appears to have begun with the death of a 37-year-old woman from the village of Kubu Sembelang on May 4.

Since her death, several of the woman's blood relatives have tested positive for the virus and seven have now died.

The latest death is the woman's 32-year-old brother, who died on May 22; it seems he was closely involved in caring for his son, a 10-year-old boy who died on May 13.

It appears that three of the confirmed cases stayed overnight in a small room with the initial case when she was symptomatic and coughing frequently.

According to the WHO, sequencing tests have shown no evidence of a significant mutation in the bird flu strain responsible for the deaths.

The deaths have raised concern that the virus is being transmitted from person to person.

The WHO says all the confirmed cases in the cluster can be directly linked to close and prolonged exposure to a patient during a phase of severe illness.

Though the Indonesian cluster is one of the largest to occur since the disease re-emerged, such clusters have appeared before among family members, most recently in Turkey and Azerbaijan.

Some experts have suggested the cluster could mean there is some genetic feature in the family's make-up that rendered its members more vulnerable to the strain.

While the source of that outbreak hasn't been officially confirmed, investigators suspect the victims were engaged in the practice of de-feathering swans which is an illegal activity and surviving family members may have tried to hide it from authorities.

Bird flu has spread rapidly since late 2003 from Asia to Europe, the Middle East and Africa. Earlier this month Djibouti reported its first human case of H5N1, the first confirmed human case in the Horn of Africa.

Since 2003, outbreaks have been confirmed in more than 48 countries and territories, according to data from the World Organisation for Animal Health (OIE).

Thirty countries have reported outbreaks since the beginning of January 2006, mostly involving wild birds such as swans.

Countries with confirmed human deaths are: Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Thailand, Turkey and Vietnam.

To date according to the WHO since late 2003, the virus has sickened at least 217 people in 10 countries, killing 123 of them.