IIRC the Voyager was a Hiker with an added iodine stage, so they could call it a purifier and not just a filter. I also seem to recall there was some controversy as to whether this actually worked against viruses.

From what I can find on the intertrons, a Hiker cartridge will fit a Voyager (buried somewhere in the Katadyn FAQs). Whether this would be worth it or even necessary is anybody's guess. If the filter in question was stored dry, then it's just fine. If stored wet it could be mildewed.

Cheers,
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--Rick