HongKang is a memory resident parasitic virus. It hooks INT 21h and writes itself to the end of .COM and .EXE files that are executed or accessed by DOS functions FindFirst/Next FCB (DIR command). The virus has a bug and cannot infect files under "standard" DOS.
On April 7 it decrypts and displays the message:
Celebrate HongKang return to CHINA 1997 !
The virus then deletes files instead of infecting them.