I have killed a couple with them in the last 30+ years of squirrel hunting.If wasting one squirrel every now and then is keeping you out of early season hunting then you are missing out.I have only saw a couple that were infected and they have a nasty sore and knot on their neck,I feel that killing them may have been better than them dying from the sore getting infected.Just get out and hunt,take a pair of binocularsand observe the animal a minute or two if possible and you may see the sore and might choose not to shoot it.Good hunting.