To study the impact space travel has on viruses, Nasa researchers analysed blood, urine and saliva samples from astronauts before, during and after space shuttle flights and International Space Station missions.
The findings, recently published in the journal Frontiers in Microbiology, show an increase in the shedding, or reactivation, of these viruses while in space.
Lead study author Satish K Mehta from Johnson Space Centre said: “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.
“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.”
According to researchers, the reactivation of the dormant viruses was found to be caused by stress – the same factor that awakens them on Earth.
In addition to being confined to small spaces and separated from family and friends for extended periods of time, astronauts also undergo stress during takeoff and re-entry, at which point they are also exposed to zero gravity and cosmic radiation.
The study found that four of the eight human herpes viruses were detected, including oral, genital, shingles and chickenpox.
However, although the viruses were found to “wake up,” most of the astronauts did not display symptoms.
“Only six astronauts developed any symptoms due to viral reaction,” Mehta said. “All were minor.”
In addition to the increased possibility of infecting others, the reactivation of the herpes virus raises concerns regarding future long-term missions to Mars.
“The magnitude, frequency, and duration of viral shedding all increase with length of spaceflight,” Mehta said. “The ideal countermeasure is vaccination for astronauts – but this is so far available only against chickenpox.”
Researchers are currently looking for methods of combating the reactivation of the virus – which would also benefit those on Earth.