Hello I Am Writing This Frm Bangalore. India. My Question

Hello i am writing this frm bangalore. India. my question my father has herpes zoster. I dont knw how he contracted this varicella virus. He is under medication. My dads age is 78 its almost two weeks. Since this was diagonised he has excruciating pain. We cant see him in this situation. How long will it take to normalise and pain to subside. Thank u. Hassan