# 5314
From the latest World Health Organization influenza update, we get this graphic showing the regional differences in influenza type, and activity, around the globe.
(Click to enlarge)
(Legend)
Trends that will no doubt weigh heavily on the minds of those attending this week’s WHO Consultation on the Composition of Influenza Vaccines for the Northern Hemisphere 2011-2012 where the makeup of the fall 2011 influenza vaccine will be determined.
Scientists must guess, six months in advance, which flu strains are likely to be dominant in the upcoming flu season.
Although it happens rarely, as we saw in 2009, a new flu strain can emerge after the seasonal strains have been selected, throwing a sizable monkey wrench into the fall vaccination campaigns.
While some version of the 2009 H1N1 and seasonal H3N2 viruses would appear to be obvious choices, the decision on which influenza B virus (Victoria or Yamagata lineage) to include is far more problematic.
The track record of guessing which B virus will dominate hasn’t exactly been stellar (correct about 50% of the time over the past decade).
Some researchers are promoting the idea of including both strains in the yearly vaccine (see Two Bs Or Not Two Bs?)
And complicating matters, even the H1N1 and H3N2 viruses circulating 6 to 12 months from now could have shifted enough antigenically to reduce the vaccine’s effectiveness.
The stakes are enormous, and participation is not for the faint of heart. Getting it right will save thousands of lives.
Getting it wrong . . .
Well . . . be glad it’s not your decision.
While we can only truly know if their selections prove correct after the end of the next flu season, we’ll obviously be watching with considerable interest over the coming days to see what is decided.
A few highlights from the latest WHO report.
Influenza update - 11 February 2011
Update number 127
Summary
Influenza activity is increasing on the European continent, particularly in the central, south and eastern part. In the tropics, several countries of southern Asia have seen a recent increase in influenza virus transmission mainly due to influenza A(H1N1) 2009 virus.
Other tropical areas of the world and the temperate countries of the southern hemisphere are currently reporting very little influenza circulation. Influenza transmission in North America, notably in the United States of America (USA) has increased this week with a slight increase of (H1N1) 2009 compared to earlier weeks. Transmission in most of northern Africa and the Middle East has peaked recently and is declining.
Some countries in northern Asia are seeing an increase in (H1N1) 2009 transmissions and some are seeing an increase in influenza-like illness activity. The majority of the viruses characterized from North America and Europe are closely related to the vaccine viruses for the current seasonal vaccines.
Virological surveillance
During weeks 3 to 4, widespread outbreaks of laboratory confirmed influenza A(H1N1) 2009, A(H3N2) and B viruses continued to be reported in many parts of the northern hemisphere. In general (H1N1) 2009 and B viruses predominated in Asia and Europe. In the North Americas A(H3N2) activity remained high but A(H1N1)2009 activity increased.
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