Random Analytics: H7N9 (August 2013)
by Shane Granger
***** Please note that the infographics/charts of the Avian Influenza A(H7N9) virus presented were updated with public source information to 0001hrs 13 August 2013 CET/EST *****
The recent confirmation of a H7N9 case in Huizhou, Guangdong Province was the inspiration for this month’s infographic.
During the month of July there were two confirmed cases of H7N9. The first case, with a 10 July onset occurred in Langfang with a dispersed population of around 3.9-million located just 60-kilometres from the heart of Beijing and its 20.7-million residents. The more recent case with onset 27 July was in Huizhou, with its 4.6-million citizens and just 100-kilometres from Hong Kong (population 7.1-million).
After a brief sojourn this variant has decided to randomly strike at two locations within a relatively easy drive to two extremely connected and globally linked population centres. Just these four cities alone are more than 50% more populated than the entire land mass of Australia and 1.8-million more than Canada.
The other point that I wanted to make was to highlight the temporal pattern which now has six-months of data confirmed. Since April, where 70.6% of the current onsets were recorded, only four cases (two in May, none in June and two in July) have occurred.
The Northern hemisphere summer has not killed of H7N9 although it is quiet.
The fact that H7N9 has cropped up again near global cities is pure downside risk. The fact that it is occurring during the Northern hemisphere summer is additional risk. The fact that we only have a half year of temporal data available for this emerging disease means we don’t yet have a full picture of what risk we face as we commence the colder seasons.
Autumn is upon us and Winter is Coming.
Cases by Region (including Taiwan)
There have been 135-cases reported in China, 44 of which have resulted in death. Although transported by commercial aeroplane from Jiangsu there is one case reported in Taiwan who has subsequently recovered. For the record my case numbers include the single asymptomatic cases from Beijing. The most recent onset confirmation occurred 27 July in Guangdong, the first known case from that province. The last fatality confirmation via Xinhua was reported on the 12th August.
To date 32.4% of all known cases have been fatal. For context the Case Fatality Rate of SARS was 10.9%.
The World Health Organisation confirmed that to 11 August there were 87 patient discharges (the National Health and Family Planning Commission has been doing monthly updates on the 10th of each month but the August press release is still pending). This equates to a Case Recovery Rate of 64% (with every chance for a slight improvement as there are still four patients receiving treatment). Asymptomatic cases remain at one (0.7%).
Cases by Job Title
As a Workforce Planner I am always fascinated by how disease interacts with our employment or our daily activities. This is potentially relevant in understanding how H7N9 transfers as only one case can be scientifically linked to a person-to-person transfer, although there is strong evidence to suggest at least three family clusters.
With 42.2% of cases in the 65+ cohort the greatest job title is that of retirement. Of the 106 confirmed occupations 37-cases (34.9%) are attributed to retirees who are more likely to visit traditional bird markets and potentially are more involved in food preparation at home, both with greater associated risks. I make a small point that food preparation is traditionally more likely to be done by women and there are only seven females (just 18.9%) who are ‘retired’ in my data, thus exposure to bird markets might be a greater factor in exposure.
Farmers account for 27-cases (25.5%). Given that most Chinese agriculture is still small cropping with additional poultry (chicken, ducks, geese etc.) and other livestock the high proportion is not that surprising given that it is an avian influenza.
From there the break-downs by employment don’t offer much in terms of vector assistance, outside those such as market vendors or poultry transporters that have daily exposure to feather and fowl.
It still seems that although your employment might marginally increase your exposure to H7N9 your just as likely to catch the disease by preparing a chook for the table or living within proximity of a bird market.
Acknowledgements: Thanks first and foremost to FluTrackers and the great work you do. For good journalism on this topic I follow Helen Branswell and CIDRAP. If you are interested in getting a daily feed on H7N9 (and other related topics) then I would recommend Crawford Killian’s H5N1 site. If you like more detailed analysis of H7N9 (and other viruses) then I would point you to my fellow Queenslander Dr Ian M Mackay and his recently revamped Virology Down Under blog.
Lastly, thanks to George R.R Martin and his wonderful ‘A Song of Fire and Ice’ epic for the borrowed line (books only, I don’t do ‘A Game of Thrones’ HBO series).
- Updated the main infographic and Cases by Region after a Hebei fatality was confirmed. Some minor tweaking of article after a review of the published material confirmed a further 5 patient releases. Added Helen Branswell & CIDRAP to my acknowledgements and can’t say why I didn’t do this in the first case.