Source: Global Influenza Programme, WHO/CDS/CSR, Department of Communicable
Disease Surveillance and Response, Wed 9 Mar 2005 [edited]
<http://www.who.int/influenza>


Viet Nam: a brief summary of recent analyses of avian influenza H5N1
viruses from humans
-----------------------------------------------
Since 31 Jan 2005, WHO has received more than 90 clinical specimens sampled
between 24 Dec 2004 and 29 Jan 2005 from confirmed and suspected H5N1 human
cases in Viet Nam. Antigenic and genetic analyses are being conducted in
the WHO Collaborating Center for Reference and Research on Influenza and
the WHO H5 Reference Laboratory in the National Institute of Infectious
Diseases, Japan. So far, 9 viruses have been isolated from specimens
collected from southern Viet Nam.

Results show that:

(1) These viruses belong to group Z and are genetically highly similar to
the viruses isolated in 2004, including A/Vietnam/1194/2004 and
A/Vietnam/1203/2004, which are the prototype vaccine strains recommended by
WHO for pandemic influenza vaccine production.

(2) Except for one virus, all the rest are antigenically closely related to
A/Vietnam/1194/2004 and A/Vietnam/1203/2004.

(3) At the receptor recognition site, there appears [to be] an avian
receptor preference.

The conclusions so far:

(1) Very little mutation has been observed since last year [2004].

(2) There is no need to change the prototype pandemic vaccine strain
selected by WHO last year [2004].

(3) Genetically, the viruses continue to show resistance to amantadine.

Dr. Wenqing Zhang
Global Influenza Programme, WHO/CDS/CSR
Department of Communicable Disease Surveillance and Response
1211 Geneva 27
Switzerland
<WHOinfluenza@who.int>