It seems unlikely that a young, fit former top athlete would become so seriously ill from normal flu. Yet it is not as exceptional as you might think, explains Professor Steven Callens, infectious disease specialist and head of general internal diseases at Ghent University Hospital.
“In young people, the immune system can sometimes overreact after an infection,” Callens explains. “This can lead to inflammation of the lungs, pericardium or heart muscle, which weakens the heart muscle.”
This overreaction of the immune system is called a cytokine storm: the body produces so many inflammatory substances that organs can start to fail. Paradoxically, this is more common in young people with a healthy immune system. Older people who have had the flu before are often better protected because their immune system has learned to respond more moderately.
