Influenza virus activity in the world
30 September 2013
Based on FluNet reporting (as of 24 September 2013, 13:00 UTC), during weeks 36 to 37 (1 September 2013 to 14 September 2013), National Influenza Centres (NICs) and other national influenza laboratories from 72 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 23 268 specimens. 1772 were positive for influenza viruses, of which 1360 (76.7%) were typed as influenza A and 412 (23.3%) as influenza B. Of the sub-typed influenza A viruses, 332 (31.8%) were influenza A(H1N1)pdm09 and 713 (68.2%) were influenza A(H3N2). Of the characterized B viruses, 26 (92.9%) belong to the B-Yamagata lineage and 2 (7.1%) to the B-Victoria lineage.
During weeks 36 and 37, A(H3N2) viruses was the predominant subtype detected globally followed by A(H1N1)pdm09 and influenza B viruses. Overall, influenza activity remained low in the northern hemisphere with reports of increased influenza activity from some countries in the southern hemisphere.
In Africa, influenza A(H3N2) and B activity was high in Ethiopia and the Central African Republic respectively. These viruses co-circulated in South Africa but at lower levels compared to previous weeks.
Widespread outbreaks of A(H3N2) and A(H1N1)pdm09 viruses were reported in Australia. Increased activity of both viruses was also reported from New Zealand.
Increased A(H3N2) activity was observed in China with co-circulation of B viruses. Influenza activity remained low in general in the region.
In general, influenza activity remained low in the Americas.
Two new cases of human infection with A(H1N1)v viruses were reported in the United States of America.
- Click here for information from the Centers for Disease Control and Prevention (CDC), United States of America
Following the WHO Consultation (23 to 25 September 2013) on the Composition of Influenza Virus Vaccines for the Southern Hemisphere 2014, it was recommended that the influenza vaccines for the southern hemisphere 2014 season contain the following viruses:
For the trivalent vaccine:
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A/Texas/50/2012 (H3N2)-like virus;
- a B/Massachusetts/2/2012-like virus.
It is recommended that quadrivalent vaccines contain the above three viruses and a B/Brisbane/60/2008-like virus.