Nobody likes being ill at work. Waking up with a fever, many of us would just take the day off. But what if your work happens to be 220 miles above the earth’s surface, and you live there too? This is the reality for astronauts at the International Space Station. Space flight affects the human body in many different ways, from loss of muscle and bone mass on long journeys to motion sickness, and it looks like it affects the immune system too. The team of astronauts which returned from the International Space Station this week, including British astronaut Tim Peake, brought with them data and samples which could help us understand this effect.