# 5666
According to the latest update from the World Health Organization, Influenza levels in the northern hemisphere have returned to inter-season baseline levels, and transmission of flu in the tropics is generally low.
So, for the next few months, it will be activity in the southern hemisphere that will capture our flu interests.
A few excerpts from today’s update follow:
Influenza update - 01 July 2011
Summary
• Influenza activity in the temperate regions of the northern hemisphere is at baseline inter-seasonal levels.
• Transmission in tropical areas is low overall with focal areas of transmission noted in a few countries of Central America and northern South America, western and eastern regions of sub-Saharan Africa, and tropical Asia.
• The influenza season has now started in South Africa and may be starting in Australia as well. South Africa has continued to report increasing numbers of both mild and severe cases, primarily related to influenza A(H1N1)2009. Australia has noted a recent increase in emergency room visits due to influenza-like illness and significantly increased notifications of influenza activity in the states of South Australia and Queensland.
As you can see by the map above, the mix of flu strains varies by region, with influenza B making a stronger appearance in the more tropical zones while influenza A/H1N1 appears to predominate in the more temperate regions.
One trend worth noting is that in Bolivia, influenza A/H3N2 detections have increased steadily for the past 8 weeks.
South Africa appears to be leading in flu activity, with A/H1N1 (indicated in yellow below) making up the bulk of the samples tested.
Today’s virological analysis states:
The vast majority of recently characterized viruses remain antigenically similar to the WHO recommended vaccines for the 2010-2011 northern hemisphere and 2011 southern hemisphere influenza seasons.
During weeks 23 to 24 (05 June 2011 to 18 June 2011), National Influenza Centres (NICs) from 71 countries, areas or territories reported data to FluNet*. A total of 837 specimens were reported as positive for influenza viruses, 583 (69.7%) were typed as influenza A and 254 (30.3%) as influenza B.
Of the sub-typed influenza A viruses reported, 83.2% were influenza A(H1N1)2009 and 16.7% were influenza A(H3N2).
(FluNet data as of 28 June 2011 14:00 UTC)
