Dormant viruses activate during spaceflight March 15, 2019 https://phys.org/news/2019-03-dormant-viruses-spaceflight.html Herpes viruses reactivate in more than half of crew aboard Space Shuttle and International Space Station missions, according to NASA research published in Frontiers in Microbiology. While only a small proportion develop symptoms, virus reactivation rates increase with spaceflight duration and could present a significant health risk on missions to Mars and beyond. "During spaceflight there is a rise in secretion of stress hormones like cortisol and adrenaline, which are known to suppress the immune system. In keeping with this, we find that astronaut's immune cells—particularly those that normally suppress and eliminate viruses—become less effective during spaceflight and sometimes for up to 60 days after." In the midst of this stress-induced amnesty on viral killing, dormant viruses reactivate and resurface. "To date, 47 out of 89 (53%) astronauts on short space shuttle flights, and 14 out of 23 (61%) on longer ISS missions shed herpes viruses in their saliva or urine samples," reports Mehta. "These frequencies—as well as the quantity—of viral shedding are markedly higher than in samples from before or after flight, or from matched healthy controls." Overall, four of the eight known human herpes viruses were detected. These include the varieties responsible for oral and genital herpes (HSV), chickenpox and shingles (VZV) - which remain lifelong in our nerve cells—as well as CMV and EBV, which take permanent but uneventful residence in our immune cells during childhood. CMV and EBV, are two viruses associated with causing different strains of mononucleosis or the "kissing disease".