Godzilla couldve contracted a virus from SpaceGodzilla in the previous film, right?
I first saw that view in Marrero’s book, and I take anything he writes with a healthy amount of skepticism. But you’re probably referring to an article in G-Fan #38. Basically, it states that Yuki’s blood coagulator weakened Godzilla’s immune system. SpaceGodzilla bit him, transmitting a space virus which affected Godzilla’s nuclear system.