March 25, 2019
2 min read

Spaceflight activates latent herpes viruses in astronauts, NASA study shows

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Latent herpes virus reactivation has been documented in more than half of astronauts during space shuttle and International Space Station missions, and according to a recent study funded by NASA, the cause is stress.

“Herpes virus is a broad category of viruses, beyond the small subset that cause sexually transmitted diseases. Most humans become infected early in life with one or more, and never fully clear these viruses,” Satish Mehta, PhD, senior scientist in the immunology/virology lab at the Johnson Space Center in Houston, told Infectious Disease News.

“NASA scientists have been studying the effects of space flight on the immune system for over 20 years. The reactivation of dormant viruses is not unique to astronauts. Certain childhood viruses, such as the one that causes chickenpox, are not fully eliminated from our bodies. They are controlled by the immune system and maintain a ‘dormant’ state in the different cells of the body.”

According to the study, which was published in Frontiers in Microbiology, Mehta and colleagues matched samples of blood, urine and saliva collected from astronauts before, during and after short space shuttle flights and long-term International Space Station missions with healthy controls.

Photo of an astronaut in space 
Stress contributes to the reactivation of latent herpes viruses in space.
Source: NASA

Results showed that 47 out of 89 (53%) astronauts on short space shuttle flights, and 14 out of 23 (61%) on longer space station missions shed herpes viruses in their saliva or urine samples. According to the study, astronauts shed four of the eight major human herpes viruses: Epstein-Barr, varicella-zoster and herpes simplex-1 in saliva and cytomegalovirus in urine. The researchers said most astronauts were asymptomatic, with only six developing symptoms.

“Larger quantities and increased frequencies for these viruses were found during spaceflight as compared to before or after flight samples and their matched healthy controls,” Mehta and colleagues wrote.

Mehta explained why: “[The] short answer is stress. In people with reduced immunity, such as the elderly or stressed individuals, these viruses can awaken and cause disease,” he said.

“Although NASA believes there is no clinical risk to astronauts during orbital spaceflight, there is concern that during deep space exploration missions, there may be clinical risks related to viral shedding. Although we do not have a serious clinical problem related to herpes viruses, their reactivation is an excellent ‘flag,’ or biomarker, for stress and reduced immunity.”

In the study, Mehta and colleagues noted that continued viral shedding after a flight can pose a potential risk for crew who may encounter infants, seronegative adults or immunocompromised people, so protocols have been put in place. Mehta explained that astronauts are quarantined for a short period of time after they return from space, followed by rehab and time spent with family.


“Viral shedding with no symptoms has no further implications for us to follow,” he said.

They concluded the study saying that the information collected from space studies will shape the way NASA prepares for and designs missions beyond the moon and Mars. – by Caitlyn Stulpin

Disclosures: Mehta reports being employed by Jes Tech, KBR Wyle Laboratories. Please see the study for all other authors’ relevant financial disclosures.