Evidence is mounting that astronauts are more susceptible to infections while in space. For example, astronauts on board the International Space Station (ISS) commonly suffer from skin rashes, as well as respiratory and non-respiratory diseases. Astronauts are also known to shed more live virus particles; for example, the Epstein-Barr virus, varicella-zoster responsible for shingles, herpes-simplex-1 responsible for sores, and cytomegalovirus. These observations suggest that our immune system might be weakened by space travel. But what could cause such an immune deficit?

Exposure to microgravity causes changes to the human immune system:

“Here we show that the expression of many genes related to immune functions rapidly decreases when astronauts reach space, while the opposite happens when they return to Earth after six months aboard the ISS,” said Dr. Odette Laneuville, an associate professor at the Department of Biology of the University of Ottawa, leading author of a new study in Frontiers in Immunology.

doi: https://dx.doi.org/10.3389/fimmu.2023.1171103