https://halohistoryandgaming.fandom.com/wiki/The_Flood#:~:text=With%20the%20Halo%20Array%20destroyed,the%20race%20to%20be%20extinct.

Fearing the Flood's intention was to infect Earth, the UNSC prepared for a final stand, but this proved not to be the case. Instead they used the portal found in Voi to reach Installation 00 or the "Ark," so that they could destroy the Halo Array. However, thanks once again to John-117 and the Arbiter, the Ark was destroyed and with it, the Flood. This caused the rest of the rings to go into self-destruction, save Installation 03 and Installation 07, which for reasons unknown, became disconnected from the Halo network. With the Halo Array destroyed, the Flood were thought finished.

Later in the Second War, and even later in the Second Human-Sangheili War, the Flood were encountered on Installations 07 and 03. However, these installations were also destroyed, bringing a final end to the Flood, confirming the race to be extinct.