This thread:
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
Indicates three weeks. I have read other places at least one week. That’s what I’m doing. No way I can separate for three! Maybe two. If you’ve not been washing up between groups though, could be moot since it’s carried in their dander which gets everywhere.
Thank you for your reply! How did your integration go?
Our chicks are already 7 weeks old and I've been careful to wash my hands, etc. when I'm in the coop with the adult, Marek's exposed hens. I'm wondering if it would be ok to integrate them in a few weeks (especially since the hen's dander must be flying around anyway). The chicks are outgrowing their coop and run really quickly, but I also don't want to risk them contracting Marek's tumors and dying since that was such a sad and traumatic experience last time.
I've read the post you shared (thank you!), but there's so much conflicting information out there on BYC, as well as other websites, and that makes it hard to know what the responsible thing to do is.