The Legato infection was a type of plasma plague.
In 2294, there was an outbreak of plasma plaque in isolated regions of the northern continent of Oby VI. Doctor Susan Nuress and her research associates believed that this strain might be closely related to this infection; however, in all cases, the treatment protocol for this infection failed as the strain proved highly resistant. This infection was mentioned in an etiological report. (TNG: "The Child", okudagram)