Influenza virus activity in the world
12 November 2012
Based on FluNet reporting (as of 12 November 2012, 10:15 UTC), during weeks 42 to 43 (14/10/2012 to 27/10/2012), National Influenza Centres (NICs) and other national influenza laboratories from 98 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 35 955 specimens. 1 654 were positive for influenza viruses, of which 969 (58.6%) were typed as influenza A and 685 (41.4%) as influenza B. Of the sub-typed influenza A viruses, 172 (22.3%) were influenza A(H1N1)pdm09 and 601 (77.7%) were influenza A(H3N2). Of the characterized B viruses, 30 (58.8%) belong to the B-Yamagata lineage and 21 (41.2%) to the B-Victoria lineage.
During weeks 42 to 43, increased sporadic detections of influenza viruses have been reported from the northern hemisphere. Influenza activity remained low in the southern hemisphere. Globally, A(H3N2) viruses remain the predominant circulating subtype followed by influenza B and A(H1N1)pdm09 viruses.
Sporadic influenza activity continued to be reported from a few counties in the European region. Most of the viruses detected were influenza A(H3N2) with only a few A(H1N1)pdm09 and influenza B viruses identified.
In North America influenza activity remained low. In the United States of America, five states reported local outbreaks of influenza while the remainder of the country continued to report sporadic detections of influenza viruses. Low levels of influenza activity were reported from Canada. The predominant subtype reported in the region was A(H3N2) followed by influenza B viruses and A(H1N1)pdm09 viruses.
Influenza activity remained low in Asia. All three subtypes were detected throughout the region with influenza B viruses the predominant subtype. One case of oseltamivir resistant influenza A(H1N1)pdm09 virus was reported from Singapore.
In the African region, increased A(H3N2) activity was reported in Cameroon while Ethiopia reported increased detections of A(H1N1)pdm09 viruses. Sporadic influenza detections were reported from the remainder of the countries.
In Central and South America influenza activity continued to decrease. Influenza B viruses circulated throughout the region although at a lower level than previous weeks. Influenza A(H3N2) and A(H1N1)pdm09 viruses were reported from Costa Rica and Brazil while A(H3N2) and influenza B viruses co-circulated in Nicaragua.