Whats the risk? Yes.
There is a risk. Much of that risk depends on the last time chickens were housed in the space. The longer chickens stay on soil, the more likely certain parasitic diseases are to accumulate... and the likelier these diseases are to remain. At the core of the matter is the birds' droppings and the conditions they create. As the droppings break down, they change the chemical composition of the soil which makes it suitable for the parasites. If there is a lot of dropping material in the soil from years of confined rearing, diseases endemic to poultry can remain for some time.
But these parasites have a life cycle which, when broken, ultimately leads to their demise. This is why it has always been advised to rotate your birds around the place annually and not leave them in one spot. This "sweetens" the soil and allows time for these disease agents to die off. It is the soil borne diseases that get em first....
A minimum of three years dormancy was the old fashioned rule of thumb, longer if the chickens were intensely reared on a chosen spot. Typically, it was also recommended that cover crops be planted on the former chicken areas, to further assist in the breakdown of potential chicken diseases. Raking lime into the soil can be a quick fix, but nothing beats time and the elements for killing off parasites.
As for the coop, the old fashioned method was to lime wash the interior what we call 'whitewash'. This coating is antimicrobial, and interior surfaces coated with it are close to pest and disease free. It is nearly forgotten today, however, and you would most likely have to make your own, if you are chemical adverse - and inclined to use it. It has several advantages, not the least is that it is cheap. It is also white and so makes it easier to spot problems, filth, etc. It does require annual refreshing, which has the added benefit of keeping you "in touch" with what is going on in the coop.
If you can abide common household bleach, then a 5% solution sprayed on after a through cleaning should do the job, but without the other benefts of white wash.