Edgar Cayce implied that if your body is neutral pH you can’t get viruses or bacterial infections.
Most people are acidic, as measured by urine or saliva.

Cayce recommended a diet of 80% alkalizing foods (vegetables and fruits, as long as fruits were taken without starch), 20% acidifying (grains, meat). (If you do lots of aerobic exercise, which is alkalizing, you may need a different diet).

Additional Cayce alkalization suggestions were pears, eaten with no other food, first thing in morning or before bed,
or, grapefruit juice or orange juice (8oz?) with a bit of lemon or lime, taken without any starchy cereals like oatmeal.
For OJ it was supposed to be 20% lemon juice, 80% OJ.  These days grapefruit juice is often as sweet as OJ.

There’s also a recommendation of adding 1-3 drops of Gylcothymoline to a glass of water 3 times a day until it can be smelled in the feces.

I have been trying to follow the diet a long time with some success.  But what has helped most noticeably de-acidify my urine was another Cayce recommendation of taking half a teaspoon of milk of magnesia every other night.  You can buy
unflavored food grade magnesium hydroxide powder, to avoid additives found in drug store milk of magnesium.

You should check your urine pH (buy pH strips, or a pH meter, or have your doctor order a urine pH test).
If it goes above 7 that’s too high.  (The doctor will say if it’s above 4.5 you are fine).  I find that a single binge of sweets can send my 
urine down close to 4.5 the next morning.