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Why Na Tao matters, despite apparent lack of human bird flu transmission

A reader of this Blogsite, Jonathan Singleton, asked me to comment on the recent proMED report regarding Na Tao, Vietnam.  As you may know, Na Tao is at the heart of a possible cluster of human cases of bird flu.  My previous two blogs have covered this developing situation.

The proMED report in question is below.

Influenza A (H5N1) is not transmitted from human to human


Yesterday afternoon [14 Apr 2010], at a meeting of the National Steering Committee for pandemic influenza control and prevention, Dr Tran Nhu Duong, Deputy Director of the National Institute of Hygiene and Epidemiology confirmed that influenza A (H5N1) has not been transmitted from human to human.

The investigation of the Institute on 2 cases of influenza A (H5N1) in Na Tao village, Nhu Co commune, Cho Moi District, Bac Kan province did not detect human to human virus transmission.

Reports of two investigation teams of the Institute in Bac Kan showed that the two patients were living about 100 meters apart, and they had never been in direct contact with each other.

All 33 people who had contact with the patients, including relatives, visitors, neighbors, nurses, and physicians, were tested and monitored for 16 days. There has been no case with symptoms of the disease. All the test results were negative.

Communicated by:



As we now know, there are three suspected human cases, not two.  But that is not material to our discussion.  What is material is that two persons, living about a little more than a football field's distance apart, contracted H5N1 bird flu. 

The report seems to conclude that distance alone, coupled with a lack of direct contact of one with another, eliminates the possibility of human-to-human (H2H) transmission.  That sounds logical enough.

But the larger issue -- the proverbial elephant in the room -- is this:  Has the virus itself changed enough in Na Tao, Vietnam, to allow for an easier method of transmission from avian to human respiratory cells?   If so, that disclosure would prove to be almost as big (and ultimately more potentially troublesome) than another H2H cluster.

That is a question that the Vietnamese report does not answer.

Let's consider the facts.  Three persons in one district contract bird flu.  Apparently they all contracted it via contact with diseased poultry.  That tells me that either the virus in that area of Vietnam is more potent, and/or the ability of the virus to favor human epithelial cells as much as it favors chicken epithelial cells.

We all know from reading the research papers that this proclivity toward one species or another is primarily driven by temperature.  The fact that both diseased poultry and diseased villagers have been detected in a cluster bears investigating by the WHO.  For a cluster is a cluster whenever you get multiple persons in a close area, H2H or no H2H.  Three B2H bird flu cases in one hamlet should be significant enough to want to gather many samples and look at them very, very carefully.

Reader Comments (1)

Dear Scott,

I'm ardent follower of your blog as I find your work and writing very interesting. I was wondering would it be possible for us to exchange links?

Your thoughts on this please. Thank you.


April 28, 2010 | Unregistered CommenterArkanoidl

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