It was just that in Resident Evil: Apocalypse the
umbrella corporation has a beauty product that
regenerates dead skin cells and ....
Rather than just a general similarity to zombie/living dead
causation.
I like George A Romero's 'Well this satellite crashed so it
must have been something to do with that...' explanation.
Not seen 28 Days later ... just seemed like an Omega Man
rip-off to me -- might give it a look though.