NASA Finds That Dormant Viruses Activate During Spaceflight

53% of astronauts on short space shuttle flights and 61% on longer ISS missions shed the herpes viruses.
Loukia Papadopoulos

Space travel can seem exciting to those watching from afar but it comes with many scary complications which surface when adjusting to new conditions never experienced on Earth. Now new NASA research is revealing that being in space may reactivate dormant viruses.


Herpes viruses reactivated

The herpes viruses were reactivated in more than half of the crew aboard Space Shuttle and International Space Station (ISS) 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 senior author Dr. Satish K. Mehta of KBR Wyle at the Johnson Space Center.

"This physical challenge is compounded by more familiar stressors like social separation, confinement and an altered sleep-wake cycle."

Mehta and colleagues monitor the physiological impact of spaceflight by analyzing saliva, blood and urine samples from the astronauts. What they found was problematic.

"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."

These circumstances could be further compounded by the stressful environment the astronauts find themselves in.

"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 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."


Researchers detected four of the eight known human herpes viruses including oral and genital herpes (HSV), chickenpox and shingles (VZV).

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Luckily, the viral shedding has been, for now, for the most part asymptomatic. "Only six astronauts developed any symptoms due to viral reactivation," says Mehta. "All were minor."

However, the shedding has been found to continue post flight posing a potential danger to immunocompromised or uninfected people on Earth. 

"Infectious VZV and CMV were shed in body fluids up to 30 days following return from the International Space Station," added Mehta.

In addition, as we engage in longer missions to space, the danger increases with their duration.

"The magnitude, frequency and duration of viral shedding all increase with length of spaceflight,' explained Mehta.

Countermeasures needed

The researcher argues that there is a necessity to develop countermeasures against this shedding. Ideally, a vaccination would work but for the moment this only exists for one kind of herpes: VZV.

"Trials of other herpes virus vaccines show little promise, so our present focus is on developing targeted treatment regimens for individuals suffering the consequences of viral reactivation."

"This research has tremendous clinical relevance for patients on Earth too. Already, our spaceflight-developed technologies for rapid viral detection in saliva have been employed in clinics and hospitals around the world," concluded Mehta.

The study is published in Frontiers in Microbiology.

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