# 5758
Southern Hemisphere, Where Flu Is Active right Now – Photo Credit Wikipedia
Along about this time of year we watch influenza’s progress south of the equator in hopes that it will give us some clue as to how our upcoming flu season will play out.
In terms of flu activity, August is to the Southern Hemisphere as February usually is to the North.
And so far this year we’ve seen indications that Australia is experiencing a fairly busy flu season (see Australia: Flu Season Nearing Peak – ISG). Yesterday blogger Arkanoid Legent carried a news article called Australia : Flu cases up seven-fold this year.
The latest official report from Australia’s Department of Health and Aging gives provides us with details on their influenza season through August 5th. A hat tip goes to Ronan Kelly on FluTrackers for posting this link.
Summary
- Levels of influenza-like illness (ILI) in the community continued to increase through both sentinel general practitioner surveillance systems and ILI presentations to emergency departments.
- Notifications have continued to rise nationally, with notifications highest in Queensland, New South Wales and South Australia. In recent weeks, influenza notifications have started to increase in all other states and territories. Currently the weekly number of notifications in the ACT, New South Wales, Queensland and Tasmania are above the peak frequency of notifications observed in 2010.
- During this reporting period there were 3,159 laboratory confirmed notifications of influenza, with Queensland reporting the highest number of notifications, followed by New South Wales and South Australia. The majority of virus detections have been pandemic (H1N1) 2009, with co-circulation of influenza B.
- The previously high proportion of influenza B in South Australia has started to decline with increasing numbers of pandemic (H1N1) 2009 notifications. The majority of states and territories have reported mostly pandemic (H1N1) 2009, with co-circulation of influenza B, except in Tasmania where there is mostly influenza B circulating, and Western Australia where there is very little influenza B circulating and mostly pandemic (H1N1) 2009.
- As at 5 August 2011, there have been 13,521 confirmed cases of influenza reported to the National Notifiable Diseases Surveillance System (NNDSS) in 2011. Currently the weekly number of notifications being reported nationally is above the peak frequency experienced in previous years, except 2009.
- The WHO has reported that influenza activity in the temperate regions of the northern hemisphere remains at low. Influenza transmission continues to occur in a few countries of the tropical region. After peaking in early June, influenza transmission in South Africa has declined to low levels. In New Zealand, rates of national ILI consultations are currently slightly above baseline activity levels and influenza type B is currently the predominant strain circulating.
With the notable exception of the 2009 H1N1 pandemic, confirmed flu cases in Australia are running at the highest rate since 2007.
Analysis of influenza types from sentinel laboratories indicate that the 2009 H1N1 virus leads in the number detected, followed by Influenza B and then the H3N2 virus.
The big question we face as our flu season approaches is whether the viruses in circulation remain a good match to this year’s flu vaccine.
While some `low reactor’ viruses have been reported, the latest virological summary below states that most of the viruses tested appear to be a close antigenic match to this year’s vaccine.
Antigenic characterisation has shown influenza isolates to be a close match with the composition of the 2011 southern hemisphere influenza vaccine with some viruses showing reduced reactivity, however there has been insufficient testing to date to determine any general trends.
Antiviral Resistance
The WHO Collaborating Centre in Melbourne has reported that from 1 January 2011 to 7 August 2011, one isolate (out of 1,240 tested) has shown resistance to oseltamivir by enzyme inhibition assay (EIA). A further isolate, out of a total of 7 pandemic H1N1 (2009) tested by pyrosequencing, has shown the H275Y mutation known to confer resistance to oseltamivir.
Whether Australia’s flu season will serve as a template for the upcoming northern hemisphere’s flu season is impossible to know. Influenza viruses are constantly evolving, and so the only thing predictable about the flu is its unpredictability.
However this season turns out, the CDC will tell you that The single best way to protect against the flu is to get vaccinated each year.
Vaccine supplies are already shipping, and should be ample this year. For more on the value (and wisdom) of getting the flu shot, you can visit the CDC’s recently updated page:
