How do Death Guard even operate?

Like if it's potentially fatal to even be near death guard due to the aura of rot that they unconsciously give off then how do they even operate. Like their ships for example, wouldn't the metal rust beyond repair and the electronics get full of mold and mildew and break down. How do they get new recruits if anyone who has extensive contact with them fall ill from sickness, never mind children whom they would need to mold into astrartes. If full on space marines are susceptible to their plague then a young boy would surely die upon first contact. I'm sure I read something as well that their gene seed isn't reusable because it's rotten so like how do they even perform basic military recruitment and maintain flyable craft if they are walking rot?