>If they made a column with an antibody to a viral protein that is expressed at the cell surface during infection, those cells would be captured as well.<
Good point, but that would only get infected cells circulating in the blood, not infected intestines, lungs, liver, etc
It could buy enough time to start treatment. Then again, if there is an "ominous cloud" containing infectious agents, medical services could get overloaded.
It also assumes that you know what the viral proteins are in advance.
------------- It does remind me of drinking straws developed for third world countries (or places that experienced flooding or other natural disasters).
"Mobilising LifeStraw® offers relief from the waterborne diseases of major public concerns such as Typhoid, Cholera, Dysentery and Diarrhoea. As a personal mobile water purification tool, LifeStraw® is designed to turn surface water into drinking water, thus providing access to safe water wherever you are."