It's an episode that just doesn't work.  It's particularly egregious in that Spyfall sets all this interesting stuff up, and Praxeus feels like it could, and should, follow up on this in some sort of fun way, but it just doesn't.  It does tease a pretty interesting story and mystery at first, but it winds up being an incredibly boring take on a virus story.  In hindsight, this episode, airing not long before COVID, really underestimated how interesting of a story it could have told around this type of content.  Even the Classic Series' Invisible Enemy, which isn't even great, mind you, left more of a favourable impression than this chore.  It's at least a bit better than some of the other Chibnall stories, but just barely so.

Like Orphan 55, this episode has an environmental message.  I'm not against the idea, but these stories only ever really bring them up in a rote way.  We pay lip service to the tenants of environmentalism but offer no new ideas, nothing challenging or thoughtful - just a bland and superficial take on something not really any more insightful or interesting than The Green Death, from decades before.  I expect more out of something from the late 2010s.