I would seem that they've totally abaondoned the international market to focus only on the Chinese market. It's quite common for Chinese software companies to do this, and Rising, Kingsoft and Jingmin have done the same.
The international version of Baidu Antivirus has not been updated since about April or May of 2015. They also stopped updating their other English langugage software, PC Faster, Baidu Cleaner and Baidu App Store.