Bird Flu Seems to Have Taken Deadly New Step in Indonesia

Six family members in Indonesia who died of bird flu probably infected one another with the virus after a seventh apparently contracted it from birds, raising the possibility that the virus is becoming more efficient in spreading among humans.

Officials with the World Health Organization emphasized that the family members had contracted the disease through close contact with one another, and there was no evidence the virus has the ability to spark a quick-spreading pandemic.

But the cluster of deaths in Kubu Sembelang village in North Sumatra worried officials because it involved a human chain of infection. One person appears to have passed the infection to a second person, who then passed it independently to a third, WHO spokeswoman Maria Cheng said.

Previous cases have involved only a single human-to-human transference of the virus, with the chain ending before a third person was infected.

The deaths in Indonesia are the largest cluster of human cases since the bird flu outbreak began in 1997.

“This certainly raised an alarm,” said Dr. Christian Sandrock, an infectious disease and pulmonary critical care specialist at UC Davis.

He said the chain of infections suggested that the virus may be hardier in the human body than previously thought.

The WHO said Wednesday that it was continuing its investigation of the Indonesian deaths and had no immediate plans to raise its pandemic alert level.

So far, the strain of bird flu known as H5N1 has infected 218 people, 124 of whom have died. Most of these cases resulted from close contact between people and birds.

The first member of the Indonesian family to become sick was a 37-year-old woman who probably was infected while working at a market where there was poultry, Cheng said.

The woman fell ill in late April and died May 4. Officials believe she died of bird flu, although it has not been confirmed because no test samples were taken.

Within two weeks of the woman’s first symptoms, six family members who cared for her became sick. A seventh relative became sick about a week after they did. All tested positive for H5N1. One of the infected family members survived.

The staggered timeline of infection suggests that the virus was passed in a human chain from the woman to a relative and then to another relative.

Cheng said investigators had not found H5N1 in the animals in that area, so the likely explanation is human-to-human transmission.

WHO officials have reported that a genetic sequencing of the virus found in the family does not show significant differences from other known versions.

Robert Webster, a virologist at St. Jude Children’s Research Hospital in Memphis, Tenn., said the lack of mutations suggests the cause of the chained infections wasn’t the virus, but the family members.

“This may be a unique group of people somehow uniquely susceptible,” he said.

But he said there was no way to know for sure until more conclusive tests were conducted.

“We’re all watching,” he said. “Everyone is looking to see if the virus has changed. The indications at the moment are no.”