Time.  

Sometimes all you can do is suffer thru it, until it is done.

We get one of these mass culling from virus every ~100 years.

FYI:
There are multiple reports that the higher your vitamin d levels the safer you are from respiratory issues like viruses.
https://www.dailymail.co.uk/sciencetech/article-8277775/People-low-levels-Vitamin-D-likely-die-COVID-19-infection.html

For some that means taking vitamin D supplements in Winter months. IMO
And in the summer months , get a lot of Sun between the hours of 11am & 2pm on as much of your body as possible. IMO
* 15 to 20 minutes 4 days a week is plenty if you are of light complexion,
* If your complexion is darker, then 40 minutes to 1 hour is required to get the same amount.