All along the film was self-explanatory but  it seems the latter part  is conveying something else.  At the beginning and during the entirety  the viewers  can see the desperation in the face of the man, who upon learning that the virus can't be contained proceeds to go up the  topmost part of the big ship and plans to take his own life.  One can see the great number of ships nearing an island  but  the last scene will take you by surprise, as the man  was actually in a convalescent home.  The aerial view with the island along with the ships surrounding it  reminds one of the microscopic cells earlier seen by the man.  This leads us to think that all of the earlier scenes were just in fact  all a part of the figment of the man's imagination.   Mind-boggling but very engaging, do check out this film.