Global Epidemiology with special focus on the interest in the Southern Hemisphere Temperate Zone
In the latest global pandemic (H1N1) 2009 update published on 2nd July WHO reported that as of 27th June more than 214 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including over 18,000 deaths. Overall pandemic and seasonal influenza activity remains low. Active transmission of pandemic influenza virus persists in parts of the tropics, particularly in the Caribbean, West Africa, and South and Southeast Asia. Pandemic and seasonal influenza viruses have been detected only sporadically during the early part of winter in the temperate regions of the southern hemisphere. Global circulation of seasonal influenza virus type B viruses has declined substantially and persists at low levels in parts of East Asia, Central Africa, and Central America. During the past month, seasonal influenza H3N2 viruses have been detected at low levels across parts of East Africa and South America.
The influenza in the temperate countries of the Southern Hemisphere, notably the countries with well-developed surveillance systems: Australia, New Zealand and Chile but also Argentina, South Africa and Uruguay is being monitored especially carefully over the summer using Epidemic Intelligence techniques. In Australia, Chile, New Zealand and South Africa there is only a small amount of Influenza Like Illness at present driven by pandemic A(H1N1). In Australia, Chile and New Zealand, levels of ILI are below recent historical seasonal levels and there have been only sporadic detections of seasonal or pandemic influenza virus during the first half of June 2010. This can also be seen on the WHO reporting from virological surveillance where there is a time-trend figure. I.e. this is mild compared to an ordinary 1970 to 2008 winters . However it is early days in the Southern Hemisphere winter though of course this information is reassuring as it is compatible with the pattern of the 1957 pandemic where there was only a single pandemic winter.[see ECDC Pandemics of the 20th Century]
The special interest this year is because these countries will be the first to experience the second winter of transmission with the pandemic virus. Hence they will give an indication of what Europe can expect in its winter of 2010/2011. Normally seasonal influenza illness does not start to rise until May or June in these countries.