What Causes Numbness In My Husbands Hand?

My husband has been in hospital for 3 days with suspected chicken pox although he thinks he had it when he was 5. He is covered head to toe in hundreds of blistering scabs- the most being on his hands and palms. He has experienced chronic muscle seizure last night and is now left with numbness and pins needles in his right hand which he can't close. He is on antivirals- can't get answers from hospital as to what this is until Monday as dermatology don't work weekends- he's exhausted and hasn't slept for 4 nights now. Spots started a week ago on elbow.