It is suspected that he was exposed to H7N9 while engaged in sketching / painting wilderness landscapes.
The official initial news release is at this link: http://www.zjwst.gov.cn/art/2013/10/15/art_362_395434.html
(Machine Translation Below):
There is also a report of large numbers of dead pigs, ducks, chickens and rabbits floating in a near by river (blamed on flooding). We suspect either the deaths, or the flooding (wetland increase) may be tied with the new H7N9 outbreak.