Thank you, guess I should have asked if anyone knows how long the viral shed might be around. I like the idea of 5 extra pulleys.Of course they "can". A piece of space junk "can" fall out of the sky and hit your house. You "can" have an accident the next time you drive to the grocery store. It "can" rain today.
The question is "will" they get sick from Marek's. Nobody knows. If they are exposed to the Marek's virus they certainly can. Some chickens have a nature resistance to Marek's. When Marek's hits a flock it is fairly common for about half to not be affected. Sometimes the entire flock is affected, sometimes hardly any of them. There is luck involved, both in their resistance and which strain of Marek's it is.
It is also possible that your flock will never be exposed to the Marek's virus. When I was in Arkansas I spoke with a university poultry science professor that also served on the team that investigated chicken diseases in the region. He said that in the last two years only one case of Marek's had been reported in that county and it was not near me. I know, not every case is reported if it is a private backyard flock but some are. My flock never got it.
I don't know how prevalent Marek's is where you live. If you are in the USA you can chat with your county extension office and see if they can help you find the Marek's statistics for your area. That's what I did and instead of paying to get my first flock vaccinated I got five extra pullets.