Incidence of Latent Virus Shedding During Space Flight (Latent Virus) - 08.23.18

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Incidence of Latent Virus Shielding During Spaceflight (Latent Virus) study will support and expand information on latent viruses - or those inactive in the human system - that can reactivate in space flight, such as a cold sore. Latent virus reactivation may be an important threat to crew health during extended space missions, as crewmembers live and work in a closed environment. Potential applications of this research include the development of a rapid and sensitive diagnostic method for identifying crewmembers at increased risk of illness due to viral infections. New technology from this investigation benefits both NASA and commercial applications.
Science Results for Everyone
Warning: latent viruses on board! This investigation examined DNA of Epstein-Barr (EBV) and Varicella zoster (VZV) viruses, which due to this investigation, are now easily detected in the saliva of astronauts. Inactive or latent viruses were found to reactivate inside the human body during space flight. EBV reactivation appeared to increase at all phases of space flight, while VZV increased as space flight approached and decreased post-flight. No reactivation occurred during 90-day bed rest on Earth. The stressful conditions of space flight and individual response to stress may influence this reactivation. The results could help protect the health of astronauts and the integrity of the space station.

The following content was provided by Duane L. Pierson, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Duane L. Pierson, Ph.D., NASA Johnson Space Center, Houston, TX, United States

Satish K. Mehta, Ph.D., Enterprise Advisory Services Incorporated, Houston, TX, United States

NASA Johnson Space Center, Human Research Program, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits
Information Pending

ISS Expedition Duration
November 2000 - August 2001; December 2001 - December 2002; April 2005 - October 2005; April 2006 - October 2007

Expeditions Assigned

Previous Missions
Latent Virus has been performed on many Shuttle missions, including STS-107 (Columbia), which was lost in 2003.

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Experiment Description

Research Overview

  • Risks associated with most bacterial, fungal, viral and parasitic pathogens can be reduced by a suitable quarantine period before the flight and by appropriate medical care. However, latent viruses (viruses that lie dormant in cells, such as herpes viruses that cause cold sores) already inside the cells of crewmembers are unaffected by such actions and pose an important infectious disease risk to crewmembers involved in space flight and space habitation.

  • Weakening of the immune system of astronauts that may occur in the space environment could allow increased reactivation of the latent viruses and increase the incidence and duration of viral shedding. Such a result may increase the concentration of herpes and other viruses in the spacecraft.

Latent herpes viruses pose an important infectious disease risk to crewmembers involved in space flight and space habitation. The risk certainly increases as the mission duration increases. Risks that are associated with most bacterial, fungal, viral, and parasitic pathogens can be reduced by a suitable quarantine period before the flight and by appropriate medical care. However, latent viruses are unaffected by such actions. The observed decrements in the immune response resulting from space flight may allow increased reactivation of the same herpes viruses and may increase the incidence and duration of viral shedding. Such a result may increase the concentration of herpes viruses in the spacecraft. Particulates (including viruses) do not settle out of the air in the microgravity conditions of space flight. Additional characteristics of space flight, such as living in relatively crowded conditions in a closed environment and using recycled air and water, will increase the potential for transfer of viruses among the crewmembers. This study will help determine the characteristics of viral parameters such as latent virus reactivation, shedding, and crew exchange during space flight, and is an integral part of ongoing efforts to accumulate microbiological data concerning the exposure of astronauts to potentially infectious agents.

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Space Applications
Latent virus reactivation may be an important threat to crew health during the longer duration exploration missions as crewmembers live and work in a closed environment. This investigation will aid in determining the clinical risk of asymptomatic reactivation and shedding of latent viruses to astronaut health, and the need for countermeasures to mitigate the risk. Stress-induced viral reactivation may also prove useful in monitoring early changes in immunity prior to onset of clinical disease.

Earth Applications
The viral-specific saliva DNA test currently used for space flight investigations may be applied to the rapid diagnosis of herpes virus disease in clinics. These studies of latent virus reactivation in the very healthy, superbly conditioned flight crews may provide new insight into stress, immunity, and viral disease in the general population.

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Operational Requirements and Protocols
Saliva samples are collected daily during the mission (beginning on Flight Day 2). Immediately after awakening and prior to brushing teeth, the crewmember retrieve a Collection Bag Assembly containing an unused cotton plug from the personalized Saliva Kit. The cotton plug is placed in the mouth for two minutes until the cotton plug is saturated with saliva. The saliva containing plug is placed back in the Collection Bag Assembly, the clip removed, the swab mixed with the liquid preservative, and the clip replaced. The Collection Bag Assembly is labeled with the MET and stowed in the personalized Saliva Kit Assembly in the compartment labeled,"Used". During the sample collection period, medications and stressful conditions are recorded. In the event of a cold sore, a sample of the lesion is collected with a viral Culturette.
Crewmembers collect saliva samples every other day from about 180 to 150 days before the launch (L-180 to L-150) of space shuttle, every day during flight, and every day after flight for two weeks ( R+1 to R+14). During the sample collection period, medications and stressful conditions are recorded. In addition, blood and urine samples are collected at 10 days before the launch, at landing and at the annual medical exam of the astronauts. Saliva and urine samples are analyzed using the polymerase chain reaction (PCR) to detect the presence of three important herpes viruses (Epstein-Barr virus and Varicella zoster virus (from saliva), and cytomegalovirus (from urine). The PCR technique allows the detection of both symptomatic and asymptomatic shedding. Viral antibody titers for these herpes viruses are measured by indirect immunofluoresence in plasma. Stress hormones like cortisol and catecholamines are measured in plasma and urine samples collected at different time points.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Many of the biological samples collected from astronauts before and after space flight have proven valuable for the advancement of science. Saliva, in particular, has enabled the early detection of the Varicella Zoster (VZV) and Epstein-Barr (EBV) viruses, which reactivate under the stressful conditions of space flight. Two studies with participant groups ranging from 8 to 32 astronauts, examined the DNA of VZV and EBV in saliva samples and found that both viruses reactivate inside the human body even though there is no external manifestation of the virus. A third follow-up study with 23 astronauts found that VZV, EBV, plus an additional virus – i.e., cytomegalovirus, showed an increase in frequency, duration, and amplitude of viral copies relative to shorter-duration missions in space.  The examination of herpes simplex virus type 1, herpes simplex virus type 2, or human herpes virus 6 virus showed no reactivation. A separate study exclusively examining a control sample of ground participants found that there is no reactivation of the viruses (VZV, EBV) during a 90-day bed rest. In conclusion, astronauts undertaking long-duration spaceflight experience increased latent viral reactivation. Susceptibility to these viruses is primarily detected through increased salivary cortisol concentrations. Understanding the shedding of viruses in space is important for the health of astronauts and the integrity of the International Space Station. 

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Results Publications

    Pierson DL, Stowe RP, Phillips TM, Lugg DJ, Mehta SK.  Epstein-Barr Virus Shedding by Astronauts During Space Flight. Brain, Behavior, and Immunity. 2005; 19(3): 235-242. DOI: 10.1016/j.bbi.2004.08.001. PMID: 15797312.

    Mehta SK, Laudenslager ML, Stowe RP, Crucian BE, Sams CF, Pierson DL.  Multiple latent viruses reactivate in astronauts during Space Shuttle missions. Brain, Behavior, and Immunity. 2014 June 1; epub. DOI: 10.1016/j.bbi.2014.05.014. PMID: 24886968.

    Mehta SK, Laudenslager ML, Stowe RP, Crucian BE, Feiveson AH, Sams CF, Pierson DL.  Latent virus reactivation in astronauts on the International Space Station. npj Microgravity. 2017 April 12; 3(1): 11. DOI: 10.1038/s41526-017-0015-y. PMID: 28649633.

    Mehta SK, Cohrs RJ, Forghani B, Zerbe G, Gilden DH.  Stress-induced Subclinical Reactivation of Varicella Zoster Virus in Astronauts. Journal of Medical Virology. 2004; 72: 174-179. DOI: 10.1002/jmv.10555.

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Ground Based Results Publications

    Crucian BE, Stowe RP, Mehta SK, Yetman DL, Leal MJ, Quiriarte HD, Pierson DL, Sams CF.  Immune Status, Latent Viral Reactivation, and Stress During Long-Duration Head-Down Bed Rest. Aviation, Space, and Environmental Medicine. 2009; 80(5): 37-44. DOI: 10.3357/ASEM.BR05.2009.

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ISS Patents

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Related Publications

    Mehta SK, Stowe RP, Feiveson AH, Tyring SK, Pierson DL.  Reactivation and shedding of cytomegalovirus in astronauts during space flight. Journal of Infectious Diseases. 2000; 182(6): 1761-1764. DOI: 10.1086/317624.

    Birlea M, Cohrs RJ, Bos N, Mehta SK, Pierson DL, Gilden DH.  Search for varicella zoster virus DNA in saliva of healthy individuals aged 20-59 years. Journal of Medical Virology. 2014 February; 86(2): 360-362. DOI: 10.1002/jmv.23834.

    Payne DA, Mehta SK, Tyring SK, Stowe RP, Pierson DL.  Incidence of Epstein-Barr Virus in Astronaut Saliva During Space Flight. Aviation, Space, and Environmental Medicine. 1999 December; 70(12): 1211-1213. PMID: 10596777.

    Pierson DL, Mehta SK, Gilden DH, Cohrs RJ, Nagel MA, Schmid DS, Tyring SK.  Varicella zoster virus DNA at inoculation sites and in saliva after Zostavax immunization. Journal of Infectious Diseases. 2011 June 1; 203(11): 1542-1545. DOI: 10.1093/infdis/jir139.

    Stowe RP, Sams CF, Pierson DL.  Effects of Mission Duration on Neuroimmune Responses in Astronauts. Aviation, Space, and Environmental Medicine. 2003 December; 74(12): 1281-1284.

    Mehta SK, Nelman-Gonzalez MA, Tyring SK, Tong Y, Beitman A, Crucian BE, Renner AN, Pierson DL.  Localization of VZV in saliva of zoster patients. Journal of Medical Virology. 2017 April; epub. DOI: 10.1002/jmv.24807.

    Mehta SK, Pierson DL, Cooley H, Dubow R, Lugg DJ.  Epstein-Barr virus reactivation associated with diminished cell-mediated immunity in antarctic expeditioners. Journal of Medical Virology. 2000 June; 61(2): 235-240. DOI: 10.1002/(SICI)1096-9071(200006)61:2<235::AID-JMV10>3.0.CO;2-4.

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Related Websites

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image Microscopy image of a herpes virus, one of several latent viruses that will be studied during the Latent Virus investigation. Image courtesy of Linda Stannard, of the Department of Medical Microbiology, University of Cape Town, South Africa.
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image Computer generated image of cytomegalovirus (CMV).
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image Electron micrograph of the chicken pox virus, the bar represents 100 nm. Naked capsids are seen. Image courtesy of Dr. Frank Fenner, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
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