(Xinhua)
Updated: 2004-02-10 11:28

The World Health Organization (WHO) announced on Monday more tests are needed to ensure that the avianinfluenza detected in Vietnam cannot be transmitted directly from person to person.

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

However, the WHO learned on Monday 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 virusfrom the second sister is being sequenced this week, the WHO said.

So far, the WHO has said the H5N1 strain of the avian flu virus that has killed at least 19 people in Asia can only be passed to human from contact with infected birds.

The organization has warned that the H5N1 can be highly lethal if it combined with a human influenza virus to create a new, highly contagious strain transmittable among humans.