I wasn't sure where to put this, so thought I'd try here since shedding is talked about in this study, though it seems to be mainly about persistence of the virus in the natural environment. The whole study is at the link.

https://kb.osu.edu/dspace/bitstream/...arten_2009.pdf
ENVIRONMENTAL TOLERANCE OF A H4N6 AVIAN-ORIGIN
TYPE A INFLUENZA VIRUS

A Thesis
Presented in Partial Fulfillment of the Requirements for
the Honors Degree Bachelor of Science in the
Undergraduate School of The Ohio State University
By
Charles F. Schwarten
*****
The Ohio State University
2009