9 week old sick

Anyone else already had a sick baby? I have twin girls and tonight one for them started getting a fever. 100.8. We took her to the er and they did a respiratory panel. They didn’t give her anything for her fever. She was positive for the human coronavirus or I guess the common cold. She weighs 9 1/2 pounds. Everything I have googled says she can have 1.25 of Tylenol. I tried calling the er dr back but they were less than helpful. I am going to take her to her ped in the morning. Any helpful advice or tips for getting through babies first illness?!?! Thanks!