I searched Debian's packages and it looks like they've removed Nginx from the stable distribution (Jessie). It looks to be temporary as it's still in Sid, but I can't find any information on Debian's site. Does this indicate a problem with the previously available packages? From what's on my machine, the previously available version was 1.6.2.
Here are the search results, although they're liable to change when Nginx gets reintroduced:
https://packages.debian.org/search?keywords=nginx&searchon=names&exact=1&suite=all§ion=all