Friday, 4 September 2015

To (type) B or not to (type) B...

Image adapted from Geoscience Australia,
The Australian Government.[13]
The latest weekly influenza statistics for Queensland were made public today.[1] Unfortunately there are no hard public numbers to support claims about the proportion of strains from the two influenza B lineages that affect humans that have been circulating in Queensland - for either July or August.
I was hoping to find some support for comments in the media this week which included...
The Brisbane strain has accounted for 27 per cent of influenza B cases in the year to August 23 [2]
  • This is in the latest report,[1] but these are year-to-date proportions -almost pointless for the spike in cases that happened more recently i.e. 48% of 2015 influenza cases occurred in the past 3 weeks [12]. Also not helpful when considering how few influenza Bs seem to be 'lineageanated' (have a lineage determined-further characterised - ?term)
..it was 25 per cent higher this year[3]
  • Talking about B/Brisbane strain's rise
Whatever. The upshot is that Australia has had a big influenza B virus-dominated winter in 2015. 

At least some proportion of those Bs have been due to strains of Influenza B virus Victoria-like lineage. That lineage was not included in the sponsored trivalent vaccine - namely the Brisbane strain (first characterised here in Brisbane back in 2008).[3,4,5,6] 

I had expected, based on the earlier Eurosurveillance article from our southern labs[9], that an influenza virus with an already decent presence that had not predominated in a number of years and which was not covered by the current vaccine would take off and cause a big season. But it seems like that hasn't happened. And yet we've had a huge influenza B season here in Queensland, and across Australia, nonetheless. 

Seems a strange mix to me but I'm no flu expert so perhaps this is all very normal for this Rubik's cube of a virus. Here's hoping for some literature on this down the track.

Despite the completely unavoidable mismatch event there remain a bunch of influenza A virus subtypes and the Phuket strain of the other influenza B virus lineage (Yamagata) that are indeed catered for by this season's trivalent vaccine. While the flu season may be taking a turn downwards,[1] you may want to consider a vaccination if you or your family hasn't had one yet-talk to your GP!

The newer (to us in Australia anyway), less common and not (yet?) sponsored quadrivalent vaccine caters for both influenza B virus lineages.

Figure from most recent State of Queensland (Queensland Health) report found here includes data up to 30th August 2015.[1]
Images excised from PDF and saved using Adobe Photoshop CC 2015.0.0
Click on image to enlarge
Oh, and those age bands I've discussed previously [10,11], are still the highest - school aged kids (5-19 years) got a lot of influenza B in 2015. Compare that to my earlier comparison - those age bands have really shot ahead.[11]


Figure from most recent State of Queensland (Queensland Health) report found here includes data up to 30th August 2015.[1]
Images excised from PDF and saved using Adobe Photoshop CC 2015.0.0
Click on image to enlarge
References...

  1. https://www.health.qld.gov.au/ph/documents/cdb/influenza-qld-150830.pdf
  2. http://www.couriermail.com.au/news/queensland/brisbane-flu-not-on-the-radar-but-try-telling-that-to-13000-victims/story-fnihsrf2-1227508437647
  3. https://www.health.qld.gov.au/news-alerts/news/150901-flu-brisbane-strain.asp
  4. http://www.brisbanetimes.com.au/queensland/queensland-flu-season-worst-on-record-20150901-gjc8ie.html
  5. http://www.abc.net.au/news/2015-09-01/vaccine-has-not-protected-people-from-the-brisbane-flu/6739996
  6. http://www.smh.com.au/national/health/surge-in-unusual-flu-cases-prompts-warning-from-doctor-20150814-giz6s4.html
  7. http://www.brisbanetimes.com.au/queensland/queensland-flu-season-worst-on-record-20150901-gjc8ie.html
  8. http://www.noosanews.com.au/news/surprise-flu-strain-not-part-of-this-years-vaccina/2759817/
  9. http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=21201
  10. http://virologydownunder.blogspot.com.au/2015/08/queensland-influenza-age-shift-still.html
  11. http://virologydownunder.blogspot.com.au/2015/08/queensland-influenza-sees-shift-in-age.html
  12. http://www.dailymercury.com.au/news/surprise-flu-strain-not-part-of-this-years-vaccina/2759817/