help my 11 month old sleeps too much!

Hi. my 11 month old had a high fever 39-39.5°C with vomiting for 3 days. After she had no more fever since the 26th. The problem os that she sleeps almost non stop. she sleeps 20-21 hours out of 24! yesterday for example she fell asleep at 2 PM and she slept until 7.40PM. she went back to sleep at 8.15 PM she slept without wakeing up until 9.20AM and now is 10 AM ans she already wants to go back to sleep! in the beginning I tought she is recovering from the fever but she sleeps longer and longer. I tried Google-ing but I didn't find anything. Any insights? She is very irritable and sluggish but otherwise ok.