New NASA research has revealed that dormant viruses may reactivate during spaceflight. Scientists reported that herpes viruses have reactivated in some crews involved in the Space Shuttle and the International Space Station missions.

Spaceflight And Body's Ability To Suppress Viruses

To study the physiological effect of spaceflight, Satish Mehta, from Johnson Space Center, and colleagues analyzed the saliva, urine, and blood samples collected from astronauts before, during, and after spaceflight.

They found that during spaceflight, secretion of stress hormones increases. Stress hormones such as adrenaline and cortisol are known to suppress the immune system.

Mehta and colleagues also found that the astronauts' immune cells, particularly those that normally eliminate and suppress viruses, tend to be less effective during spaceflight and even up to 60 days after that.

The researchers said that 47 out of 89 astronauts on short space shuttle flights and 14 out of 23 astronauts on longer missions at the ISS 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," Mehta said.

Viral Shedding Typically Asymptomatic

Not everyone developed symptoms. Only six astronauts have so far found to have developed symptoms because of reactivation and all were minor, but researchers said continued virus shedding after the flight has potential implications. It may pose threat to immunocompromised or uninfected individuals on Earth, such as newborns.

The researchers also warned virus reaction rates rise with the duration of the spaceflight, and this could pose problems on the health of astronauts who will embark on missions to planet Mars and beyond.

Countermeasures To Viral Reactivation

The researchers detected four of the eight known human herpes viruses. These are those responsible for oral and genital herpes (HSV), chickenpox and shingles (VZV), Epstein-barr virus (EBV), and cytomegalovirus (CMV). CMV and EBV are linked to different strains of the so-called kissing disease.

The researchers said risk of viruses reactivating during deep-space missions underlines the importance of developing countermeasures to viral reactivation.

"The information gleaned from these space studies will shape the way we prepare for and design exploration-class missions, beyond the moon and mars, where reactivation of latent viruses could result in increased risk for wide-ranging adverse medical events," the researchers wrote in their study published in Frontiers in Microbiology.