Space travel can reactivate herpes in astronauts: NASA study

A NASA study has found that dormant herpes viruses reactivated in over half the astronauts aboard the Space Shuttle and International Space Station missions. It is a result of immune system suppression known to be caused by stress hormones secreted during spaceflight. Astronauts' immune cells become less effective during spaceflight, Satish Mehta, a senior author of the study said.