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Thursday, 4 April 2013

Avian influenza – preparing to take flight?

Attention has been drawn to southeast Asia once again for an emerging novel influenza strain.  The past few weeks have seen reports of now nine H7N9 influenza cases associated with three deaths.
April 5th update - 14 cases and six deaths. 
April 10th, 33 cases, 9 fatalities.
April 14th, 49 cases, 11 deaths
April 29   115 cases, 23 cases, 9 provinces in China and first case amongst a person returning from China.  

Historically H7 strains have been associated with poultry, and outbreaks of generally mild illness have been reported  since 1999 in at least United States (H7N2),  Italy (H7N3), Canada (H7N3), the, Mexico (H7N3),  United Kingdom (H7N3, H7N2) and Netherlands (H7N7).   The Canadian outbreak in lower Fraser Valley in 2004 resulted in widespread culling of flocks, but only two human illnesses, both mild and in occupationally exposed persons.

So the nine, non-epidemiologically linked spread across cities in four adjacent provinces in China, raise new concerns about the potential for broader dissemination.  WHO surveillance has improved since the first B5 bird influenza cases back in 2000, and augmented by SARS and can be tracked at http://www.who.int/influenza/human_animal_interface/en/  .

The H7 avian influenza is antigenically distinct from H5 bird flu that has continued to creep globally since 2003 and associated with over 600 cases but a markedly high mortality rate of nearly 60% amongst confirmed cases.  To date vaccine development has focused on H5 strains with candidate options similar to the adjuvanted pandemic vaccine used in Canada as the model. 

The good news from China is intensive investigation of case contacts have not identified others with illness and only two possible clinical cases which predated a confirmed case and virus was not identified.

While innumerable emerging viral illnesses occur with few progressing to illness, monitoring activity is a routine public health surveillance for which considerable depth and expertise is dedicated within Canada, US, China and most other countries – feeding into the global efforts of the WHO.

Follow the developments on Twitter #H7N9  

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