[BostonCard]

I presume there's no way to go back and test the January swabs for COVID-19.

No, but once serology is widely available, it should be possible to test those specific patients for coronavirus antibodies.  If positive, it doesn't necessarily mean that the particular episode was definitely COVID-19, but if the patient didn't remember any other significant illnesses it would be suggestive.  If they were negative, it should prompt you to think of something else (though a false negative is always a possibility).

 BC

[BostonCard]

I presume there's no way to go back and test the January swabs for COVID-19.

No, but once serology is widely available, it should be possible to test those specific patients for coronavirus antibodies.  If positive, it doesn't necessarily mean that the particular episode was definitely COVID-19, but if the patient didn't remember any other significant illnesses it would be suggestive.  If they were negative, it should prompt you to think of something else (though a false negative is always a possibility).

 BC