# 5042
With the end of the declared pandemic, the World Health Organization has dropped back to providing a global flu update to once every 2 weeks.
This report – current as of week 42 – was released on Nov 8th.
H3N2 continues to be the predominant player around the world, and in most countries, is overshadowing the 2009 H1N1 strain.
Influenza B is circulating as well, and is particularly prevalent in the southern hemisphere as a late-season strain.
Some excerpts, but follow the link to read the whole thing.
Description: Displayed data reflect the most recent information reported to FluNet, WHO regional offices or on ministry of health websites in the last 2 weeks.
The percent of specimens tested positive for influenza includes all specimens tested positive for all influenza subtypes. The pie charts show the distribution of virus subtypes among all specimens that were tested positive for influenza.
Influenza - Update 120
Worldwide, overall influenza activity remained low, except in parts of the tropics, most notably in Southeast Asia, and to a lesser extent in the tropical areas of the Americas. After late winter and springtime influenza epidemics in several countries of the temperate southern hemisphere, influenza activity has returned to near or below baseline in most places.
Notably, however, a recent post-season rise in cases has been noted across parts of southern Africa associated with localized outbreaks of influenza H1N1 (2009) virus.
Seasonal influenza A(H3N2) viruses continued to be the predominant circulating type or subtype of influenza viruses worldwide, however, in addition, in many countries there has been co-circulation of seasonal influenza B viruses and to a lesser extent, influenza H1N1 (2009) viruses. The latter has been recently predominant in a limited number of countries, including in India.
Virological surveillance
The WHO Global Influenza Surveillance Network is constantly monitoring the evolution of influenza viruses. Like other influenza viruses, the influenza H1N1 (2009) viruses have being undergoing genetic evolution. Since their emergence, variants having substitutions at residues 125/142, 222 and/or 374/391 in the haemagglutinin gene have been detected. Recently other genetic mutations have also been reported.
However, antigenic characterization to date has shown that all these viruses are not antigenically distinguishable from the vaccine virus A/California/7/2009.
FluNet reports
During weeks 41 to 42 (10 -23 October, 2010), National Influenza Centres (NICs) from 31 countries reported data to FluNet*. A total of 1,749 specimens were reported as positive for influenza viruses, 1,512 (86.4%) were typed as influenza A and 237 (13.6%) as influenza B. Of the sub-typed influenza A viruses reported, 15.6% were influenza H1N1(2009) and 84.0 % were influenza A(H3N2).
The number of countries, regions, and territories reporting since the height of the pandemic has dropped by nearly 2/3rds, but the following gives some indication of the relative distribution of virus strains reported in the northern hemisphere since mid-summer.
As you can see, H3N2 (light blue) has been the predominate strain identified in the northern hemisphere since early August, while the 2009 H1N1 strain (yellow) has declined.
Past performance is no guarantee of future results, but the upward trend in the H3N2 virus over the past few months has some observers concerned that we may see a tough flu season ahead.
Years where H3N2 dominates tend to be more severe than years where H1N1 is the major strain in circulation.
The good news is, it isn’t too late to get your flu shot.
This year’s shot provides coverage for both the 2009 H1N1 and and the Perth H3N2 strains, along with a B strain.
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