The exterior shot of the asteroid which USS Voyager goes in to chase the Vidiian ship is the exact same exterior shot of the asteroid where the Enterprise-D locates the USS Pegasus in The Pegasus (1994)
This is the first of several times The Doctor uses the phrase "I'm a doctor, not a...", a catchphrase that was made famous by Dr. McCoy in Star Trek (1966).
In this episode the term 'phage' is used for a virus that attacks animal cells. 'Phage' is short for 'bacteriophage', a virus that specifically infects bacteria and archaebacteria.
The subterranean Vidiian corridor was a reuse of the hidden corridor that crew members find behind a holographic barn in Caretaker (1995).
The aliens were originally known as "the Phages." Their name was later changed to "Vaphorans," which they were called even in the shooting script. The change to "Vidiians" was not made until after the episode was written.