Washington: Space travel caused herpes viruses to reactivate in more than half of crew aboard Space Shuttle and International Space Station (ISS), according to a NASA study, a finding that could jeopardise mankind’s future missions to Mars and beyond.
While only a small proportion develop symptoms, virus reactivation rates increase with spaceflight duration and could present a significant health risk on future missions.
“NASA astronauts endure weeks or even months exposed to microgravity and cosmic radiation — not to mention the extreme G forces of take-off and re-entry,” said Satish K Mehta at NASA’s Johnson Space Center.
“This physical challenge is compounded by more familiar stressors like social separation, confinement and an altered sleep-wake cycle,” said Mehta.
To study the physiological impact of spaceflight, researchers analyse saliva, blood and urine samples collected from astronauts before, during and after spaceflight.
“During spaceflight there is a rise in secretion of stress hormones like cortisol and adrenaline, which are known to suppress the immune system,” said Mehta.
“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,” he added.
In the midst of this stress-induced amnesty on viral killing, dormant viruses reactivate and resurface, according to the research published in the journal Frontiers in Microbiology.
“To date, 47 out of 89 (53 per cent) astronauts on short space shuttle flights, and 14 out of 23 (61 per cent) on longer ISS missions shed herpes viruses in their saliva or urine samples,” said 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,” he said.
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.
PTI