Recombinomics: Clade 7 H5N1 In Beijing Raises Pandemic Concerns

Commentary

Clade 7 H5N1 In Beijing Raises Pandemic Concerns
Recombinomics Commentary 20:06
January 6, 2009

Gene sequencing by the National Avian Influenza Reference Laboratory indicated that this virus is very similar to the avian influenza virus variant isolated in Shanxi in 2006.

A 19-YEAR-OLD Beijing woman who suffered the city's first human case of bird flu since 2003 has died, municipal health authorities said yesterday.

The sequencing comments above are from the OIE report on the H5N1 from the Jiangsu outbreaks last month, followed by the most recent confirmed human case in China (see updated map), who died yesterday. The “virus variant” is clade 7, as seen in phylogenetic analysis of A/chicken Shangxi/02/2006 in the latest WHO on vaccine targets. On the same branch is A/Beijing/01/2003, which was isolated from the first H5N1 confirmed case in mainland China.

It is likely that the latest case was also infected by clade 7 H5N1, which is vaccine resistant because most vaccines target clade 1 or 2, which are significantly different than clade 7.

The details of the Jiangsu outbreaks are unclear. Some local media reports suggested the outbreak was large and involved dead poultry that was shipped to market. Other reports acknowledged the H5N1 infection, but noted that the infected birds were asymptomatic and identified through routine screening.

However, if the latest case was fatally infected by clade 7 from an asymptomatic duck, then the potential for additional cases is high because the virus can travel and dispress undetected. Moreover, since clade 7 is resistant to the most common vaccines, it could be widespread.

Clade 7 was also reported in Vietnam in August, and a clade 7 target was recently identified by the WHO. There currently is no clade 7 pandemic vaccine, and the selected target is only proposed as a target, as indicated in the most recent WHO vaccine update. The earlier presence of clade 7 in Vietnam may be related to the recent confirmed human case in northern Vietnam, which was announced today.

Thus, more detail about the H5N1 in Beijing and Vietnam, including sequence data from these isolates, as well as the WHO vaccine target, A/chicken/Vietnam/NCVD-016/2008, would be useful.

The presence of vaccine resistant H5N1 in asymptomatic ducks in Beijing would create significant pandemic concerns.

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