it is possible to diagnose or more correctly detect any defined illness or pathology.
Right through the key board or a device screen?
Physical sensors can provide a wealth of real time data on every networked user. Movements and contacts are a matter of record. Viruses or pathogens that change human behavior, reproductive drives and sexual orientation are evident long before obvious physical symptoms appear.
Tiny signs invisible to most humans are road flares to a Convolutional Neural Net just as it they are to non human species that see heat from sensor pits located in the facial region
What an enemy can tell about us through touch screens and keyboards goes well beyond our searches for 'red lesions on penis' or ' best remedies for black buboes' "HCQ for sale"
if an entity is able, as all big tech/ social media cos and many nation states are
we can look at a life time of data for any individual. We can tell when eyesight gets worse or better, when breath volume improve or deteriorates – whatever, it is trivial to track any illness in currently available data with currently available technology.
consider the implications.