Virus Memo - The reason for the lack of formalities in the beginning paragraph was originally because there was not enough time to do so. The English version indicated that it was because they go "way back" (this was probably added in to highlight that Wesker got the serum from Birkin). In addition, the English version strongly indicated that the Prototype Virus actually revives the host from the dead so long as some part of the host remains upon being infected, while in the Japanese version, it's repeatedly made clear, even among the 10% that never wake up, that the infected host only enters suspended animation from the start, never actually dying beforehand. The file also specifies in the Japanese version that it should be utilized in an "assumed emergency," while the English version condenses it to being "as needed." The virus in the Japanese version mentioned it as a "mutant strain" of another virus, while in the English version Birkin indicates he stole it from a mutant stock.
Brian Irons Profile - Brian Irons being twice accused of attempts at rape during his college years is replaced with his being twice accused of domestic violence against his wife during the same event. This was most likely done as an act of censorship, due to the serious subject matter. A similar edit would later occur in Resident Evil: The Darkside Chronicles, via the file Brian Irons (file).
In the "Rebirth 2 ending", Wesker's comparison with the phoenix was added into the script.