In medieval times, knowledge about the causes of disease was limited, so there was little chance of preventing it.
There were very few doctors. In the early medieval period, most of them were educated men from the higher ranks of society who learned through practice rather than by attending a medical school.
By the late Middle Ages, however, anyone wanting to become a doctor had to train at one of the medical schools that were opening across Europe, eg in Oxford University in 1220. These trained doctors were often known as 'physicians'.
In Wales, the most famous medieval doctors were the physicians of Myddfai, a family who passed down medical knowledge over the generations from the 13th to the 18th centuries. They made herbal remedies, operated on wounds and used astrology to treat their patients.
Attempts by doctors to prevent disease were limited for a number of reasons.
They relied heavily on observation and questioning of the patient. They could listen to the lungs, or take a pulse, but had no medical instruments to help diagnosis. They carried posies, oranges or lighted tapers with them to counteract the miasmas which they thought spread disease.
They used urine charts to help diagnose illness. Urine was thought to contain any excesses of bad humours so, after inspecting urine for colour, smell or sometimes taste, they would attempt a diagnosis.
Treatments were based on the theory of the four humours. Keeping the humours in balance, they thought, would prevent illness, or help treat a patient who was ill.
They called on astrology to determine the best treatment. It was believed the position of the moon and planets influenced the humours and when patients should have blood let.
The Church taught that everything was divinely inspired by God, and that illness was a punishment for evil. Church leaders were suspicious of anything scientific, as it might challenge the authority of the church. When the priest, Roger Bacon, suggested that doctors should do their own research instead of accepting what Galen had said, church leaders put him in prison for heresy.
There was some progress in the Middle Ages, but it was limited.
These were set up in universities, such as Padua and Salerno in Italy, and Oxford in England, to train doctors in medicine. However, these taught the works of Hippocrates and Galen and did no new research. Padua University alone insisted that doctors visited the sick during their training.
Muslim doctors, such as Avicenna (Ibn Sīnā), began to challenge errors made by Galen and others and developed new ideas. However, because the Christian Church was at war with Islam, Muslim ideas spread only slowly to western Europe.
On the whole, medieval doctors had a poor reputation. During the Black Death, in particular, many were criticised for avoiding their patients for fear of catching plague themselves.