Well ask him how he's feeling. If he does have a cold ask what symptoms he's had. I don't know if he would be open to take a test if he is sick. If he won't then just stay away for a bit maybe. You could also just warn him about it for future information. A face shield and mask would also probably make gutting the deer a bit less unpleasant. So it's not like there is no benefit to it. I hope no one you know gets sick. I hope this dies out in deer.