'Bird flu' could have spread among two humans, WHO reports

While seeking to avoid raising undue alarm, the United Nations World Health Organization (WHO) today reported that avian influenza, or “bird flu,” might have spread from a Vietnamese husband to his sister and wife earlier this year.

Dr. Klaus Stöhr, who is leading WHO's response to the epidemic, described how at the end of last year, a family in Viet Nam had been cooking for a wedding party. The husband and one of his sisters prepared a duck on 3 January, and he fell sick on 6 January. Subsequently, the sister who prepared the duck with him also became ill, as did another sister who lived in the household as well as the husband's wife.

Lab samples from these cases were limited to only the two sisters, and so far, “what we found was that there was no other explanation for the case in one of the sisters and the wife, so we have to assume there may have been some human-to-human transmission,” Dr. Stöhr told a press briefing.

While not ruling out the spread among people, he stressed that “This virus has not changed its characteristic epidemiological behaviour.”

The latest developments, he said in response to questions, did not ratchet up WHO concern. “There is no further increase in the level of preparedness,” he noted. “We are still at pandemic phase zero - we have no pandemic.”

“This small cluster which we cannot fully understand, we can consider this as an epidemiological anomaly perhaps, which we only bring up and investigate in the absence of another better explanation,” he stressed.

“The thing is still in the box, it hasn't come out,” he said. “If we sit on the lid, it will stay there, and we still have that window of opportunity open and nothing has changed in comparison to last week.”

Asked about pandemic scenarios, he said it was possible that the virus would gradually mutate, changing characteristics so that it would be able to spread among humans rather than just from birds to humans.

“The other way these viruses could perhaps obtain the genetic information for that human-to-human transmission possibility is by re-assortment,” he said, explaining that the avian viruses “perhaps would multiply in a cell while at the same time, human influenza viruses would exist and then the genetic information would be mixed.” Those new viruses would contain both the genetic information of the human influenza as well as the avian influenza virus. That would be “a more rapid step,” he added.

Another scenario would be that “the avian virus would gradually change over time and then we would have a gradual increase in human-to-human transmission.”