# 4502
A pretty clear representation of the decline of influenza A activity around the world is included in this week’s virological update from the World Health Organization.
The full WHO update may be read here.
The chart below is just one of several you’ll find at The trend of proportions of different type and subtype influenza viruses infecting human [pdf 46kb]
While the overwhelming majority of influenza A viruses sampled proved to be novel H1N1, influenza B is the main type of flu being detected around the world.
Pandemic (H1N1) 2009 - update 96
Weekly virological surveillance update
16 April 2010 -- Overall influenza activity has remained at low level in most parts of the Northern Hemisphere. Little activity has been reported in the Southern Hemisphere in 2010 to date. In most countries where human infection of influenza virus was reported, the pandemic influenza A(H1N1) continues to be the predominating influenza A viruses subtyped (100% in Canada and the United States and 81.3% globally).
Seasonal A(H1N1) viruses were detected very sporadically in Russian Federation. Sporadic influenza A(H3N2) activity was reported from some countries including China, Japan, Russian Federation, Singapore and Thailand . Influenza B was reported as predominating influenza virus accounting for 68.6% of all influenza detections in Russian Federation, 72.7% in Cameroon, 88.7% in China, 95.2% in Republic of Korea, and 100% in Mongolia. Increased sporadic influenza B activity has also been observed in some other countries including Italy, Kazakhstan, Latvia, Singapore and Sweden.
Based on FluNet reporting for the week from 28 March to 3 April 2010, the total number of specimens reportedly positive for influenza viruses by National Influenza Centres (NIC) from 33 countries was 1,665. Of these, 355/1,665(21.3%) were typed as influenza A and 1,310(78.7%) as influenza B.
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Antiviral susceptibility surveillance has been conducted by the WHO Global Influenza Surveillance Network (GISN) including WHO CCs. So far, pandemic A(H1N1) specimens and isolates from at least 92 countries have been tested. The data showed that oseltamivir resistant pandemic A(H1N1) viruses are sporadically detected with rare onward transmission. So far, 285 cases of oseltamivir resistance have been reported by GISN and other partners. All of these viruses showed the H275Y substitution and all remain sensitive to zanamivir. (See below to obtain more information on oseltamivir resistant viruses).
