Mustaine revealed the tentative timeline for the new LP in a recent conversation with American Songwriter.
The Sick, The Dying... And the Dead has been in the works for several years now and was mostly recorded in the summer of 2019, while Mustaine was being treated for throat cancer.
It was unclear how close the album was to being released before the coronavirus pandemic in 2020. Mustaine suggested that some of it makes reference to how the world changed last year.
"The [title track] itself was a historical journey of how the plague started and where it went, starting with rats on ships carrying the disease, coming ashore in Sicily," Mustaine said.
Musically, Mustaine said he went deep into his archives to piece together a few of the arrangements.
"A lot of the riffs have been saved over time," he said. "A brand new song can be made up of something I wrote when I was 15 or 55. If It's a good riff, I'll save it."
What remains unclear about the new record is whose bass playing will ultimately make the cut. While guitarist Kiko Loureiro and drummer Dirk Verbeuren each recorded on the album, Megadeth terminated co-founding bassist Dave Ellefson last spring.
Despite Ellefson's parting request that his bass be left on the final version of the album, Mustaine confirmed this summer that the band had hired a new bassist to redo Ellefson's parts.