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Influenza B Rising

 

 

 

# 4386

 

 

While pandemic H1N1 continues to be reported in many areas of the world, the levels being seen today are far lower than what was reported a couple of months ago.  The other seasonal strains (H1N1 and H3N2) are being reported only sporadically around the world.

 

The question on everyone’s mind is; what (if anything) will rise to fill the void?

 

Over the past few weeks, reports of influenza B infections have been steadily increasing, particularly out of Hong Kong and China.   The short course on influenza B from the CDC reads:

 

Influenza Type B

Influenza B viruses are usually found only in humans. Unlike influenza A viruses, these viruses are not classified according to subtype. Influenza B viruses can cause morbidity and mortality among humans, but in general are associated with less severe epidemics than influenza A viruses. Although influenza type B viruses can cause human epidemics, they have not caused pandemics.

 

The chart(s) below show that of the 2076 samples recently tested by FluNet that proved positive for influenza (week of Feb 6-13), more than 50% were Influenza B.

What this portends for the future is unknown, since the start of the flu season in the southern hemisphere is still several weeks away.  Will H1N1 make a comeback? 

We’ll have to wait and see.

 

 

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(blow up of last 3 months)

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Here then is the latest influenza virological surveillance report from the World Health Organization.   You’ll find additional information in Pandemic (H1N1) 2009 - update 89.

 

 

Weekly virological surveillance update

26 February 2010 -- Pandemic influenza A(H1N1) 2009 infections have continued to decrease in most countries of the Northern Hemisphere in recent weeks. Little activity has been reported in the Southern Hemisphere in 2010 to date. In nearly all countries where human influenza infection is reported, the pandemic influenza A (H1N1) continues to be the predominant subtype among all influenza A viruses subtyped (87.3% in North America region, AMR, 94% in EUR and 90% global). Seasonal A(H1N1) viruses continue to be detected very sporadically. Sporadic influenza A(H3N2) activity has been reported from some countries in recent weeks. Influenza B activity continued to increase in China and Hong Kong SAR China.

 

Based on FluNet reporting for the week from 6-13 February 2010*, the total number of specimens reportedly positive for influenza viruses by NIC laboratories was 2,076. Of these, 1,003/2,076 (48.3%) were typed as influenza A and 1,073 (51.7%) as influenza B. Of all sub-typed influenza A viruses, 90% (781/866) were pandemic A(H1N1) 2009. Hong Kong SAR China has reported increased influenza B activity in recent weeks accounting for 56.1% of all influenza detections in the reporting week, while in China it accounted for 83.5%.

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