Viral evolution in the cosmos

Space travel exposes human beings to unique environmental stressors (e.g., radiation, microgravity) and induces significant physiological changes in hosts, profoundly impacting host–virus dynamics and creating conditions conducive to viral evolution. This chapter reviews current knowledge on viral behavior and evolution within the space environment, considering human, animal, plant, and spaceflight-associated viral sources. We discuss how spaceflight factors, coupled with host immune dysregulation, metabolic and hormonal shifts, altered cellular characteristics like membrane fluidity, and mitochondrial dysfunction, can influence viral replication, latency, transmission, and genetic variation. The well-documented reactivation of latent human herpesviruses (e.g., cytomegalovirus , Epstein-Barr virus, varicella-zoster virus, herpes simplex viruses) during space missions serves as a critical example of these effects, highlighting health risks within the confined built environment of spaceflight, which itself fosters unique viral transmission and coevolutionary scenarios. Methodologies for molecular diagnostics, genomic surveillance, data management and open data sharing, and advanced computational modeling, including phylodynamics, deep mutational scanning, and AI-based protein structure prediction, are explored as essential tools. Finally, strategies for mitigating viral risks during and after space missions are considered, alongside the broader implications of this research for long-duration space exploration, planetary protection, and terrestrial planetary health, emphasizing the critical need for continued investigation into viral adaptability in extraterrestrial settings.