Can't hide it if it's in his medical records, and the person has access to said records - if they're playing around with genes & virii, they need to know what they're playing with. It wouldn't surprise me, even, if there was a flag in his personnel record along the lines of "presence of pseudoelf gene markers, watch for possible development of magical abilities." It would be highly classified, of course, but give him a CO who's irrational about such things and too damnfool stupid to tell the difference between "friendly and gregarious" and "spineless" and I could see Gabe getting ridden constantly. One too many comments about how his family are elf-lovers, particularly if he were coming off an unsuccessful mission...

CO: "Maybe you wanted this mission to fail, Cameron. Maybe you're soft on the elves. You wouldn't be the first one in your family to..."
Gabe: ROAAARRRRRR!!!!!!
CO: *hauls ass / has said ass saved by Gabe's surviving teammates*