Arthur Tudor, Prince of Wales (1486-1502) was Henry VII eldest son. He was heir to the throne of England, and he had just married the Infanta, Catalina (Katherine) of Aragon. The Tudor Dynasty had never looked so secure, and when the young couple were sent to Ludlow in December 1501, the king and queen of England must have been full of hope that the new family would prosper. Unfortunately that hope was not to last. On the 2nd April 1502 Arthur died suddenly in Ludlow Castle of what was known in the sixteenth century as the sweating sickness, an almost flu like sickness that took hold very quickly. It could also be deadly, and surviving the first twenty four hours was very important.
In the past many historians have attributed Arthur's premature death at the age of 15 to him being sickly, and although this opinion has changed in recent years, some still believe that this was the reason behind Arthur's death. What is rarely mentioned is that Katherine of Aragon was ill at the same time, but happened to survive. Sweating sickness was also rife in Ludlow in 1502 and so it is likely that both Arthur and Katherine caught it. I am certain that Arthur could not have been that sickly child! The records that survive do not mention other illnesses, and due to the importance of the prince's rank such things would have been recorded. The king and queen, Henry VII and Elizabeth of York were happy to send their son and daughter in law to Ludlow in December 1501. If Arthur had been prone to illness it is not likely that the king would have wanted to risk his son's health by sending him to Ludlow, known for being damp and cold. This is seen in his attitude to Henry, duke of York who was not sent to Ludlow after Arthur's death because he did not want to lose another heir. I suspect if there was any concern for Arthur's health then he would have been kept in London after the wedding of 1501.
Arthur's death also had consequences. His younger brother Henry would become heir and in 1509 upon the death of Henry VII, he became Henry VIII. Henry VIII's contribution is well known, and whereas I am not a great fan of counter-factual history, sometimes I do wonder what would have happened in England if Arthur had lived.
If you are interested in knowing more these sources in particular are invaluable.
Garrett Mattingly, Catherine of Aragon, (London: Cape, 1942)
Steven Gunn, and Linda Monckton (eds.) Arthur Tudor, Prince of Wales, Life Death and Commemoration, (Woodbridge: Boydell, 2009)