Or the fact that an ex-Kaspersky employer implicated the company with letting out false viruse detection data (to nail their copying comptetitors).
Or the fact that ALL anti-virus software makers will NOT detect automatically their own country's secret service intentional spying software. Some are required by law not to detect their own secret service's software.
Even F-Secure is now saying that IF the new (in discussion) law in Finland passes into power, F-Secure will continue to do behind the scenes work with the Finnish Secret Police and will NOT automatically detect their viruses/keyloggers/trojans, UNLESS some other party reports it to them.
So, even if you use Antivirus software, you are better of using two (from separate countries, with different engines - one active/one on-demand) and combining that with safe-hex + some form of sand-boxing.
Yes, privacy and security has become rather cumbersome in this day and age (at least on Windows).