A super-intelligent smallpox virus, Leezle Pon was a member of the Green-Lantern Corps assigned to Sector 119. Leezle Pon was incapable of attending regular meetings of the Corps on Oa, as he ran the risk of infecting the other Green Lanterns.
Following the resurrection of the Green Lantern Corps, Leezle Pon rejoined the Corps and gained a new sector partner, Reemuz. Some time later, Despotellis, the sentient biovirus of the Sinestro Corps, infected 85% of the planets in Sector 119, including Reemuz's homeworld. Reemuz himself was among the casualties, and Leezle Pon was devastated by the loss of his partner and so many in his sector. During the Sinestro Corps invasion of Earth, Despotellis infected the Earthman Guy Gardner. Doctor Soranik Natu discovered Despotellis within Gardner, and injected Leezle Pon into Gardner. Desiring vengeance, Leezle Pon quickly went to battle with the Despotellis cells, eradicating the majority of them and capturing Despotellis in the process. Leezle Pon then took Despotellis back to Oa, where Soranik Natu began working to find a vaccine for him.