A genome sequencer was a device which could map viruses.
In 2154, Denobulan Doctor Phlox suggested to Klingon Dr. Antaak that he advise his Klingon superiors to steal a genome sequencer. This was because they were attempting to find a cure for the Klingon augment virus and Phlox was appalled at methods Antaak's superiors had gone to in their efforts to do so, Phlox considering them highly unethical. (ENT: "Affliction")