The Loque'eque were a species that originated in the Delphic Expanse. Several centuries prior to 2153 they lost the ability to reproduce and their species began to die out. In an attempt to save their race from total extinction, the Loque'eque engineered a mutagenic virus which transformed the DNA of other species into their own.
The virus also contained genetic memory. Aliens who were infected with the virus communicated in the Loque'eque language, experienced hallucinations and an extremely powerful urge to seek the Loque'eque's home city, Urquat. The Loque'eque civilization was lost but the virus was successful and as of 2093, alien Commander Tret's people had lost tens of millions to the Loque'eque virus.
When an away team from the NX-class starship Enterprise beamed down to the Loque'eque homeworld in 2153, three of the four officers were infected with the virus. Fortunately, Doctor Phlox was successful in synthesizing an antidote, returning Captain Jonathan Archer, Lieutenant Malcolm Reed and Ensign Hoshi Sato to their Human forms. Tret's people were still fighting the virus in 2153 using starships patrolling the system and away teams on the Loque'eque homeworld, literally incinerating any host of the virus. (ENT: "Extinction")