It’s been a very slow start to the H7N9 season (=spillovers from infected poultry to susceptible humans) in China. Why it’s been so slow is unclear.
The Hong Kong (HK) Centre for Heath Protection (CHP) has officially put in writing their earlier announcement of a new case; a fatality in a 72-year-old man.I wonder if the biggest A/H7N9 season to date – 2016/17 – left fewer of those most at risk of acquiring the poultry virus susceptible to infection than in the past. This most at risk being people in proximity/contact with live infected poultry (or less often, infected people).
In other words, perhaps more of those attending the live poultry markets were infected and became immune last season.
But that theory would also mean lots of unreported mild or asymptomatic H7N9 infections occurred in order to reduce the pool of susceptible humans enough to effectively halt cases. That isn’t the normal picture we have for H7N9.
Perhaps our picture is incomplete.
Perhaps China has routed the advance of H7N9 among its poultry.
Perhaps there is a better reason altogether.
- Avian Influenza Report, HK CHP