Update: Antarctic Winterover as an Analog for Spaceflight Immune Dysregulation
Orbital spaceflight perturbs the human immune system significantly; Natural Killer (NK) and T-lymphocyte (T) cell functions are most susceptible to spaceflight-induced impairment. This loss of function may manifest in persistent latent virus reactivation (CMV, EBV, VZV), which does occur at a higher frequency in astronauts compared to earthlings.
Makedonas, George↗