It's an interesting one, isn't it? And definitely gets credit for originality. It didn't all work perfectly for me but I loved the look of the monster and that they made a serious attempt at a credible and original story.

I can't think of an earlier entry in the "infected astronaut returns a changed man" premise other than Night of the Blood Beast, which never clicked for me (and I love most of Corman's 50s movies). Some of the later movies with a similar premise were among the worst too (Creeping Unknown, Frankenstein Meets the Space Monster, Monster a Go Go).

Who would have thought a freak typhoon would have come out of nowhere and wrecked all calculations?