Is it possible, then, that many people experience heart damage without knowing, and go on to recover naturally?

Endurance sports such as marathon running and extreme triathlons can cause lasting heart damage among elite athletes, research has suggested.

However, the authors said that the risk was acceptable and that the majority of the heart damage could be reversed with treatment.

But used long-term it can cause impotence, anaemia and heart damage.

Scarlet fever responds to penicillin and should always be treated aggressively to prevent rare but serious complications such as kidney and heart damage.