For general GI health:  Consume 4 oz. Kefir milk once or twice daily and a 5000IU Vitamin D3 daily. Shoot for a 25-OH Vitamin D level of 80-90nmol/L. (Your Doc can check this)

Quick Treat Protocol: 
Have bottles of 1000mg Vitamin C and 1000IU Vitamin D3 handy, as well as at least 2-3 bottles of flavored Kefir milk of choice. Kefir milk can remain good in a refrigerator for 2-3 months.

On the first hint of clinical symptoms (and the earlier the better) Immediately take an initial loading dose of 2000mg of Vitamin C and 2000IU Vitamin D3 with 4 of Kefir milk.
In one hour, take the second dose of 1000mg Vitamin C and 1000IU Vitamin D3 with 4 oz of Kefir,  and then
Every two hours, take the doses of 1000mg Vitamin C and 1000IU Vitamin D3 with Kefir to complete 3 more doses.

Patients are significantly improved or completely well within 6-8 hours in most cases.
For any mild residual symptoms, can repeat the protocol the following day.

This Quick Treat Protocol is inexpensive, without significant risk, and can see any significant clinical improvement in a very short period of time. No other treatment options are being currently offered at this time, regardless.  Any patient sent home to quarantine should consider a quick try of the protocol. Has worked in the past on colds, influenza and unspecified infections over the years we have been recommending it.
If nothing else, psychologically this protocol empowers individuals to assume an active role in their care, rather than simply having to wait passively at home in quarantine to see if you either live or perhaps die.

But mainly, it really works!  This protocol proved to be effective against the Swine Flu in 2009 (yet another coronavirus), so will hopefully prove equally as effective against this our current coronavirus pandemic.

Heal your Microbiome and Save the World.