DS9 "When it pours..."

BASHIR [on monitor]: I was running a scan on the sample you left when I noticed something unusual.

ODO: Unusual in what way?

BASHIR [on monitor]: The disease that's killing your people. You're infected. My guess is you became infected the last time you Linked with the Female Shape shifter.

KIRA: Are you sure about this? He doesn't have any symptoms.

BASHIR [on monitor]: So far. But from what I can tell, the virus is replicating quickly and it may not be long before symptoms start to surface.

Section 31 infected odo with a disease so that he would spread it to the founders and the part of that statement that Bashir said about the female founder infecting him was not true it was actually the opposite.

BASHIR: Hang on, hang on, I'm just trying to figure out when Odo became infected. I analysed the sample he left and mapped out the life cycle of the virus. I'm programming the computer to calculate just how long it took for the virus to achieve its present level of concentration.

O'BRIEN: That makes sense. According to that, he was infected over two years ago?

BASHIR: More than that. I just don't understand. I assumed he became infected when he Linked with the female shape-shifter.

O'BRIEN: But if it happened that long ago, how come he hasn't shown any symptoms before?

BASHIR: Good question. Got it. Stardate four nine four one nine.

O'BRIEN: Almost three years ago.

BASHIR: Wait a minute. Four nine four one nine. That's the day that Odo was at Starfleet Medical.

O'BRIEN: You sure?

BASHIR: Yes. My god. No wonder Hilliard wouldn't let me see the file. Section Thirty one must have created the virus, infected Odo, and then used him as a carrier.

O'BRIEN: So that when he Linked with another changeling, he'd pass it on, and eventually the entire race would be infected.

BASHIR: Thirty one isn't just trying to stop us from finding a cure. They're trying to cover up the fact that they set out to commit genocide

So we know Section 31 created it. We also know that it was two years in the past. Odo didn't show any signs for those two years, and after his bonding with the female changeling she became infected and showed signs fairly quickly.

She showed signs before Odo did and he was infected two years before her.

Bashir said in the episode he couldn't figure out why Odo showed signs later when he was infected so much earlier.

Do we ever learn why Odo showed signs of the disease later when he contracted it two years earlier?

  • 3
    It's a common trope in fiction (and in real life) that disease carriers will often not show symptoms until after the people they're infected.
    – Valorum
    Jul 23, 2015 at 5:49
  • 12
    Odo was a carrier. Carriers are designed to stay healthy for as long as possible, and infect as many as possible. He probably was given a limited dose of a "cure", or some other retardant. Biological terrorism 101
    – Petersaber
    Jul 23, 2015 at 7:06
  • Wasn't there a statement to the effect that the more times you shapeshifted, the sooner the disease showed up? Jul 23, 2015 at 13:31
  • 3
    @OrganicMarble Odo shapeshifted very little on screen. Off camera he was probably constantly changing shape while listening to Morn drone on and on and on. Jul 23, 2015 at 17:13

3 Answers 3


Section 31 designed the virus so that Odo would be a vector but not be actively infected, in order to hide the crime they committed. (This worked, but only up to a point.)

Bashir comes to this conclusion in a later episode, "The Dogs of War":

BASHIR: Odo, there is something you need to know. When I first discovered that you'd become infected with the morphogenic virus, I assumed you'd contracted it from the Founders.

ODO: Didn't I?

BASHIR: No. The fact is, it was you who transmitted the disease to them.

ODO: But how did I get it?

BASHIR: You were deliberately infected.

ODO: By whom?

BASHIR: Section 31. They used you as a carrier, hoping you would pass on the disease to the Founders. I'm sure you were never meant to develop symptoms.

ODO: I don't care whether they meant to kill me or not. The reality is the Federation set out to destroy my people.

Bashir's conclusion is logical, considering that Section 31 did not want itself or the Federation to be tied to the infection of the Founders.

As for why Odo did eventually show symptoms, Odo was taxing himself towards the end of the war with frequent shapeshifting. From "Tacking Into the Wind":

GARAK: My approach may have been quiet, but I assure you, I had no intention of sneaking up on you. My apologies. If I may ask?

ODO: Why have I deteriorated so rapidly? I've been assuming dozens of different forms over the past few weeks. Changing shape seems to accelerate the progress of the disease.

GARAK: Perhaps you should stop.

ODO: And do what? Lie here waiting to die? I came to work and work is what I'm going to do.

Granted, Odo is speaking about why the disease is accelerating in him, but we can surmise that his general shapeshifting had been increasing over the course of the war, and the protection Section 31 gave to Odo from the virus eventually failed because of this.

That being said, Section 31 probably reckoned that Odo would join the Great Link or merge with another shapeshifter yet again at some point, at which time any symptoms he might develop could be attributed to that most recent link. This is indeed exactly how things played out, before Bashir pieced together the truth.

The exact technical details of how Section 31 engineered the virus so that Odo would be immune are unknown. Nothing about this is mentioned in the episodes or in any writer's guides / notes, nor is it referred to in the DVD commentary for Season 7. There seem to be no further speculation in the novels either.

  • 1
    To explain why he eventually developed symptoms at all, my headcanon is that anything Section 31 put in him was eradicated when he was turned human by the Founders, so both the nesting virus and whatever countermeasure was in place to keep him a useful carrier only. After that, he was reinfected by his own virus (!) when he did later link with a Changeling. Then add on the rapid acceleration towards the end due to frequent metamorphosis and the timeline all adds up. Oct 11, 2018 at 14:35

Odo later said that shape shifting seems to make the disease progress faster, so since Odo didn't shape shift as much as the founders, the disease showed up later.He spent most of his time as humanoid, occasionally reverting back to jelly as part of his regeneration cycle.


He was changed into a solid and then back to a changeling. It is generally accepted that this is the reason Odo did not show any symptoms for such a long time. Being changed to a solid and then back to a changeling would most likely of altered his morphogentic matrix in some way, meaning that any changes that Section 31 made to the virus to ensure Odo would not show any symptoms would be ineffective, and the virus would attack Odo the same way it did all other changelings.

This also explains why all the other changelings show symptoms before Odo.

  • 2
    Do you have any sources to back this up? The already accepted answer says something different and quotes sources for it. Jan 11, 2018 at 8:41
  • 1
    @Fabian there is no accepted answer?
    – Edlothiad
    Jan 11, 2018 at 8:44
  • Sorry, overlooked it. I mean the first one (with the 10 upvotes). Jan 11, 2018 at 9:00
  • @FabianRöling This answer could do with some sources, but no sources given in Praxis's contradicts it. Oct 11, 2018 at 14:37

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