Ian M Mackay wrote an update on his Virology Down Under article on Wednesday where he nailed a Wave-2 data-point that I had completely missed. H7N9 snapdate: age with time. Key excerpt:
The interesting line to watch is that of the youngest age group (0-19-years) which has lifted to comprise 50% of cases in the week beginning 27-Jan. Also, the proportion of cases in the oldest age group (70->90-years) has dropped down in the past 2 weeks.
There have been a rash of children in recent announcements; 8 of the last 45 cases have been <10-years of age. For a virus with a median case age sitting at 58-years, this is quite a departure.
Is this due to an increase in familial clusters? Does it herald a shift in the way the virus is spreading? Interfamilial transmission may provide a hint at increasing transmission efficiency. It might also be a sign of increased testing augmenting clinical observation of close contacts of ill family members.
It was such an interesting thought I started to dig a little deeper into the recent data to see if there were any possible interfamilial patterns that, as yet, might not be confirmed as family clusters but would have a high likelihood of being so.
Looking at the Flutrackers.com case list and case number #285 (37M) and #289 (2F). Data points:
- Onset within 5-days of each other;
- Hospitalised 2-days apart;
- Confirmed one day apart;
- Both are named Liang, although the original translation was Liang Yijun which might stand for ‘someone Liang’. As Crawford Kilian put it Liang is one of the top 100 Chinese surnames;
- Both come from Sanjiao Town (original reports had them at Triangle Town but I linked that to Sanjiao Town via local hotel addresses).
The important point to my thinking is that these two cases are the first reported in Zhongshan in both waves. Zhongshan is different from other cities in that it doesn’t have County level administration but rather six inner districts and 18 smaller surrounding towns. Sanjiao Town has a population of just 121K, which by Chinese standards is miniscule.
I don’t believe in coincidences and there is a lot of data which is missing from this picture.
Yet, as we see a lot of P2P denial occurring could we also be seeing the first of many unconfirmed family clusters?
Is this the ‘tip of the iceberg’?