Hi (His or Her name)
Subject (Requesting to take leave due to fever)
This is X (your name + Designation) wish to inform you that due to sudden high fever followed by vomiting, I have no choice, but to take urgent leave.
The doctor advised me to take complete rest for 3 days from 19th January, 2018 till 21st January, 2018.
I will be highly thankful to you, if you oblige
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