Once Nico got the confirmation nod from Max, she sent the navigation message, infected with the retrovirus, to every one of the Co-Operative vessels at the same time.
The others might not know what was going on, but they also didn't know that their ships were infected, so they would still have everything connected to the data network unless they actually took the warning from this ship seriously.
The chances of them doing that seemed pretty slim, given the ragtag, civilian lack of organization that Max had seen so far, but they could always be warned that they needed to reconnect to the ship to cleanse their devices.
"Alright, the message has been sent, so the ships should be starting to self-cleanse right now. Give them a while, and we should be able to reconnect to the ship computers and let the retrovirus reach all the devices on the ship.