FLU NEWS SCAN: Northern Hemisphere flu rise, off-season flu in Australia

Nov 26, 2012

Flu starts its Northern Hemisphere rise
Flu detections are increasing in some Northern Hemisphere countries, but so far levels haven't exceeded seasonal thresholds or marked the beginning of flu season, according to a Nov 23 update from the World Health Organization (WHO). Areas seeing increased activity include southern regions of the United States and Canada's Ontario province. In Europe, flu detections are still low, but sporadic activity has been reported in Austria, Belgium, the Czech Republic, Finland, France, Germany, Norway, and the United Kingdom. Elsewhere, Cambodia has reported rising flu activity, and some circulation has been noted in Middle Eastern countries, with 2009 H1N1 as the most commonly detected virus. In the Southern Hemisphere, flu activity continues to decrease to interseasonal levels. Globally, H3N2 remains the dominant flu strain, followed by influenza B and the 2009 H1N1 virus, the WHO said in a separate virologic assessment.
Nov 23 WHO update
Nov 23 WHO virologic assessment

Study: Off-season flu surge in Australia not caused by genetic shift
An increase in out-of-season influenza cases in Australia's spring and summer of 2010-11 was not caused by genetic differences in viruses but probably reflected a "natural variation" in virus circulation, according to a study today in Influenza and Other Respiratory Diseases. Australian investigators analyzed nationwide data from the WHO FluNet surveillance tool, state notifications, and Google FluTrends. For the state of Victoria, they used lab-confirmed flu cases and influenza-like illness proportions. They noted that the increase in notifications about flu were most pronounced in tropical and subtropical Australia. They also noted that out-of-season notifications in temperate Victoria were more than five times the average of the previous three years even though ILI proportions in the spring and summer were similar to the those in the previous years. They reported, however, that all out-of-season viruses tested were antigenically and genetically similar to those tested during the 2010 and 2011 flu seasons. They conclude that the increase in spring-summer cases "probably reflected a natural variation in out-of-season virus circulation, which was amplified by increased laboratory testing."
Nov 26 Influenza Other Respi Viruses abstract

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