Watching the "Conspiracy" episode again (S1:E25 of The Next Generation), I noticed that one of the Admiral beams up to the Enterprise in an attempt to infect number one with one of the parasites.

I thought that the beaming capability of the Enterprise had a system to detect foreign bodies that appear in a person's body and prevent the transfer when such is detected.

Would a symbiotic parasite, opposed to microbes, not be detected?

Or was that small mistake allowed for a better plot in that episode?

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    I believe you mean episode 25. Given that DS9 regularly depicted Dax being transported around in both Jadzia and Ezri with no ill effects, I would assume that the biofilters only apply to bacteria and other very small pathogens.
    – Kevin
    Commented Sep 28, 2022 at 21:15
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    @Kevin the fact is DS9 retconned the Trill as depicted in TNG - the TNG trill was terrified of the transporter because of the filter. So yes it is basically an inconsistency - but I suppose one would have to check when biofilters got established in canon - probably the "Naked Now" but a parasite is much bigger than a virus. Commented Sep 28, 2022 at 22:31

2 Answers 2


In "Unnatural Selection" (S2:E7), the crew talks about the transporter's biofilter. The discussion gives the impression the biofilter only filters out known pathogens, or at least is not 100% effective in eliminating all threats.

TROI: Well I suggest we beam them both back onto the ship. Commander Data is most likely immune and surely the biofilter will...

O'BRIEN: The transporter's biofilter won't protect us. The boy was transported twice already and still infected Doctor Pulaski.

LAFORGE: Couldn't we adjust the biofilter? We could alter the filter to screen out whatever it is that's causing the disease.

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    You don't want your gut microbiome stuck in the transporter's spam filter. Commented Oct 26, 2022 at 13:08

It's possible that either the writers hadn't thought that far ahead concerning how transporters detected and dealt with foreign bodies (if they did at all), or they just let it go for the sake of story, kind of like in the episode Haven, where at the end they couldn't beam back Wyatt from the Tarellian ship without bringing the plague back with him.

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    It's possible, sure, but can you offer any evidence that this was actually the case?
    – Valorum
    Commented Sep 29, 2022 at 3:50

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