The World Health Organization (WHO) has received the results from a study of virus isolated from a 23-year-old woman who is part of a family cluster in Vietnam under investigation as the first possible instance of human-to-human transmission.

"Virus genetic material from this woman, as for the other case in this cluster, is of avian origin and contains no human influenza genes," it said in its website on Thursday.

On Feb. 6, WHO reported the results from genetic sequencing of H5N1 viruses taken from two sisters in a family cluster in Vietnam. The sequencing announced by it showed that the two viruses were both entirely of avian origin with no human genes, indicating the viruses had not become adapted to be easily transmitted from one human to another.

WHO has corrected that the virus from only one sister has been sequenced, not both sisters. The second virus sequenced and reported was from another case in Vietnam. The virus from the second sister is being sequenced this week.

(Xinhua News Agency February 12, 2004)