Microbes & infection
Also: Host-microorganism interactions
Hostile/Closed EnvironmentImmune & HematologicIn-flightLEO long-durationMars transit & surfacePublicClinicianResearcher
- Infections occur in flight but have been manageable with current measures. ◆◆◆◇ Moderate · F
- Spaceflight can change microbial virulence and host immunity. How these combine on long missions is uncertain. ◆◆◇◇ Low · F M
Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.
NASA risk title (verbatim)
Risk of Adverse In-Mission and Long-Term Health Effects and Performance Effects Due to Host-Microorganism Interactions
NASA short title: Microhost · HRP element: Human Health Countermeasures (HHC) · Status: Active [current research ongoing] [1]
What it is
This risk covers infections and other health effects that come from how crew and microbes interact in a closed spacecraft [1].
Current evidence
- Monitoring shows opportunistic pathogens on spacecraft [1].
- Infectious events happen in flight, but current countermeasures limit most of their impact [1].
- Past research shows changes in crew immunity and in microbes, including their virulence. Either could change how likely or how serious disease is [1].
- On the 3-day Inspiration4 mission, most microbiome changes were short-lived. Shifts in the oral microbiome lasted longer and tracked with immune gene activity [4].
NASA’s risk posture
NASA scores each risk for each design reference mission (DRM) as likelihood × consequence (LxC). Both run from 1 (lowest) to 5 (highest) on the HSRB’s 5×5 matrix [1][3]. Each score comes with a disposition, such as “Accepted”, “Requires Characterization” or “Requires Mitigation”. These ratings were last approved by NASA’s Human System Risk Board (HSRB) in 12/2024 [1].
| Mission | Duration | In-mission (operations) | Long-term health |
|---|---|---|---|
| LEO | Short (under 30 d) | 2x3 · Accepted | 2x2 · Accepted |
| LEO | Long (30 d–1 yr) | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Lunar orbit | Short | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Lunar orbit | Long | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Lunar orbit + surface | Short | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Lunar orbit + surface | Long | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Mars preparatory | Under 1 yr | 2x3 · Accepted with Monitoring | 2x2 · Accepted |
| Mars planetary | 730–1,224 d | 4x3 · Requires Mitigation | 4x3 · Requires Mitigation |
Copied from the Human Research Roadmap on 2026-10-14. Ratings change. Check the live record before citing.
Open knowledge gaps
NASA lists 7 knowledge gaps for this risk, 7 of them open as of 2026-10-14 [1]. Each gap ID links to its page on the Human Research Roadmap (HRR).
Show NASA’s gap list (verbatim)
| Gap | NASA gap statement | Status |
|---|---|---|
| Micro-101 | Evaluate the effects of isolation, confinement and weightlessness on changes in the vehicle microbiome, the human microbiome, and microbial virulence. | Open |
| Micro-102 | Evaluate whether deep-space radiation has an additive or synergistic effect with weightlessness/isolation/confinement on microbial types, numbers, and virulence. | Open |
| Micro-103 | Evaluate whether atmospheric composition, such as elevated CO2 levels or mildly hypoxic exploration atmospheres, are a significant contributor to changes in the microbial profile of spaceflight. | Open |
| Micro-201 | Micro-201: Evaluate the contribution of changes in microbial numbers, types, and virulence on the likelihood and consequence of adverse health events (infection), during the mission. | Open |
| Micro-202 | Micro-202: Evaluate the contribution of changes in microbial numbers, types, and virulence on the likelihood and consequence of non-infection-based effects on health and performance, including: decrease in cognition/mood/performance/BBB function related to the change in the gut’s microbiome and gut-brain axis (collaboration with HFBP), increase in cardiovascular health risks, effects of change in gut microbiome on metabolism of nutrients, correlation with inflammation | Open |
| Micro-301 | Identify, develop, and implement in-flight microbial monitoring/diagnostic tools for support of research and crew health during Gateway, Lunar, and Mars missions. | Open |
| Micro-401 | Test, optimize and validate existing terrestrial or novel technologies that can maintain in-flight microbial counts, types, and virulence at terrestrial equivalent levels. | Open |
See also Open questions.
Active countermeasure research
- Strategy. NASA’s aim is to monitor and mitigate spaceflight-related changes in the microbial community [1].
- Open gaps. These cover characterizing changes in microbes and in host–microbe interaction, in-flight monitoring tools, and technologies to keep microbial levels safe (Micro-101 to Micro-401) [1].
Project-level detail, including status, investigators and results, is in the NASA Task Book and on each HRR gap page.
Clinical articles
For practical, clinic-facing guidance, see:
Evidence profile
- Overall certainty
- ◆◆◇◇ Low (proposed)
- Evidence types
- F · Flight dataM · Model / animalE · Expert / operational / standards
- Literature through
- 2026-10-14
- NASA source
- Human Research Roadmap risk page (last published 05/13/25; read 2026-10-14)
Requirements referenced 1
| Requirement | Title | Plain-language meaning |
|---|---|---|
| [V1 3003] | In-Mission Preventive Health Care | Monitoring and prevention during flight (fitness, sleep, SANS, venous patency, immune function, dysbarism prevention). |
IDs as published in NASA-STD-3001 Vol. 1 Rev C (2023-09-15) and NASA-STD-3001 Vol. 2 Rev F (2026-07-14). NASA-STD-3001 binds NASA programs; it is not a regulation for commercial flights. Paraphrased. Standards quick reference.
References 4
- NASA Human Research Roadmap. Risk record: “Risk of Adverse In-Mission and Long-Term Health Effects and Performance Effects Due to Host-Microorganism Interactions”. Accessed 2026-10-14. humanresearchroadmap.nasa.gov/Risks/?i=80 NASA E
- NASA Human Research Program. Evidence report for the Host-Microorganism Interactions risk (2022). humanresearchroadmap.nasa.gov/evidence/reports/Host_Micro%20… NASA E
- Antonsen EL, et al. Updates to the NASA human system risk management process for space exploration. NPJ Microgravity. 2023;9:72. doi:10.1038/s41526-023-00305-z PMID:37679359 Peer-reviewed E
- Tierney BT, et al. Longitudinal multi-omics analysis of host microbiome architecture and immune responses during short-term spaceflight. Nat Microbiol. 2024;9:1661–1675. doi:10.1038/s41564-024-01635-8 PMID:38862604 Peer-reviewed F
Machine-checked on 2026-10-14: each URL resolved, each DOI's title/journal/year matched via Crossref, and claims were checked against the source text (abstract or full NASA page). Human verification against full text is still required before review. NASA documents are U.S. Government works (public domain) and are summarized with attribution; journal articles are summarized, not reproduced.
Article info
- Authors
- Pending (AI-assisted draft)
- Reviewer
- Pending review
- Last reviewed
- Pending review
- Literature through
- 2026-10-14
- AI-assisted
- Yes (disclosed)
- COI
- Pending
- License
- CC BY-SA 4.0
- Use
- Educational only · Disclaimer
- Cite this version
- Pending first edition