The transwarp network was destroyed in 2378 when Kathryn Janeway's counterpart from 2404 was able to infect the Queen with a neurolytic pathogen, an act which interfered with the Queen's ability to regulate the shielding protecting the interspatial manifolds. This in turn allowed the crew of the USS Voyager to fire a series of transphasic torpedoes, destroying the manifolds and causing the network to collapse. (VOY: "Endgame")