H7N9 by sex and week...are female cases on the rise?

I tip the hat I'm not currently wearing to CIDRAP's excellent staff writer, Lisa Schnirring for the idea that led to this chart. 

Click on image to enlarge.

I've plotted 163 of the 164 lab-confirmed H7N9 cases (includes surviving and fatal cases) by the sex of the H7N9-positive person and the week in which they acquired their illness (if date of onset was noted), or else the date the case was reported to the world. 

The chart above shows that overall, male cases dominate the H7N9 landscape each week (69.5% of all cases are male)....except that among the new appearances of H7N9 in China, there seems to be a greater number of weeks in which females are equally represented among the cases. While the case numbers are low this still begs the question, as does the cause of the apparent start of the H7N9 season, what is driving these patterns?