I saw two cases today in which the lymphocyte count was raised.
Not massively, but had doubled in a day or so. Both were in patients who had
recently been admitted to hospital.
It would seem that transient lymphocytosis related to stress has been identified as "a thing"... I'm sure I've seen this happen in the past. It is now recognised...
Transient atypical lymphocytosis in patients with emergency
Transient stress lymphocytosis