NASA has issued a warning about space herpes after a study found the virus was reactivating in crew aboard Space Shuttle and International Space Station missions.

According to the agency, while only a small proportion of the astronauts develop symptoms as a result of the dormant virus awakening, it could spell danger for longer spaceflight missions - for instance to Mars.

"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 Dr Satish Mehta.

"This physical challenge is compounded by more familiar stressors like social separation, confinement and an altered sleep-wake cycle," added Dr Mehta, senior author of the paper and academic at the Johnson Space Centre.

The research is published in the journal Frontiers in Microbiology and concerns the reactivation of the virus, rather than a new virus which had developed in space.


NASA's thorough medical systems measure the physiological impact of spaceflight by analysing astronauts' saliva, blood, and urine throughout spaceflight.

"During spaceflight there is a rise in secretion of stress hormones like cortisol and adrenaline, which are known to suppress the immune system," the study found.

"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."

Image: NASA has put more people in space than any other agency

Due to this suppression of the immune system, the astronauts' bodies are less able to keep dormant viruses down, allowing them to reactivate.

"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," reported Dr 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."

"Only six astronauts developed any symptoms due to viral reactivation," said Dr Mehta. "All were minor."

There are eight known herpes virus, including the strain for chickenpox, which once contracted will stay within their hosts' nerve cells for their entire life.

They are mostly kept suppressed by the immune system, but if the immune system itself is suppressed by space exploration, then they could pose a significant risks to astronauts travelling to Mars or beyond.

The research found that the longer the spaceflight mission, the more it seemed the viruses were reactivating.