How easy is ork contamination
I'm currently reading through the Eisenhorn omnibus, almost done with the second full novel, and I've been thinking about the short story the whole omnibus begins with. Eisenhorn is on a planet having a look into some murders the local authority believe to be cult related (SPOILER COMING UP NEXT), but in fact its a couple of da boyz who are coming through some kind of warp portal, hunting a couple hoomanz and then heading home. Eisenhorn dispatches the orkz, closes the portal and everyone is happy. My questions is, is this world now doomed? Is a couple of orkz visiting every week or two for a few hours enough for the fungus to contaminate? And if yes, how long does it have?