I agree that it can't be infectious. I had a similar problem once when moving into a rental and found there are some enzyme based cleansers that really work on old blood stains. I used one with Miracle in its name, a liquid marketed mainly for cleaning up pet messes, and it took it all out even though standard carpet cleaning services had not been able to put a dent in it.
Thanks I seen the CDC thing state that it can't live for four days I just didn't know cause the size
I mean it might not be blood its a decent size stain..could be food. I mean if it was blood some one was bad off and there's no drips around it. But I just wanted to make sure and see if it could be infectious
No risk, but I would let the realtor know...yuck.