What was unique about the recent bird-flu cases recently reported in Indonesia?

The source was not found (no dead birds or infected ones). This MAY mean that the virus was trasmitted without birds, which means it can spread by human, so there will be soon a big epidemic. However, it was also found out that the virus in these victims did not mutate.What was unique about the recent bird-flu cases recently reported in Indonesia?
A family of eight infected with bird flu in Indonesia likely passed the disease among themselves, but health officials said on Wednesday there is no reason to raise the pandemic alert level.





It is the fourth and largest family cluster of bird flu cases likely transmitted from person to person since the start of the outbreak in Hong Kong in 2003, World Health Organization spokesman Gregory Hartl said.





But this case may mark the first time bird flu has passed from person to person to person, a top US health official said.





The previous clusters all involved someone who was infected by a sick bird and then spread the virus to others. This new cluster appears to involve a cascade of transmission, said Julie Gerberding, director of the US Centers for Disease Control and Prevention, in a telephone briefing from Geneva.





The family members' close physical proximity is probably responsible for the spread of the disease.