From its earliest days, following the edicts of Jesus, Christianity encouraged its devotees to tend the sick. Priests were often also physicians. According to the historian Geoffrey Blainey, while pagan religions seldom offered help to the infirm, the early Christians were willing to nurse the sick and take food to them, notably during the smallpox epidemic of AD 165-180 and the measles outbreak of around AD 250; "In nursing the sick and dying, regardless of religion, the Christians won friends and sympathisers".[6]

Following the First Council of Nicaea in 325 AD, Christianity became the official religion of the Roman Empire, leading to an expansion of the provision of care. Among the earliest were those built ca. 370 by St. Basil the Great, bishop of Caesarea Mazaca in Cappadocia in Asia Minor (modern-day Turkey), by Saint Fabiola in Rome ca. 390, and by the physician-priest Saint Sampson (d. 530) in Constantinople, Called the Basiliad, St. Basil's hospital resembled a city, and included housing for doctors and nurses and separate buildings for various classes of patients.[7] There was a separate section for lepers.[8] Eventually construction of a hospital in every cathedral town was begun.

Christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals after the end of the persecution of the early church.[9] Ancient church leaders like St. Benedict of Nursia (480-547) emphasized medicine as an aid to the provision of hospitality.[10] 12th century Roman Catholic orders like the Dominicans and Carmelites have long lived in religious communities that work for the care of the sick.[11]

Some hospitals maintained libraries and training programs, and doctors compiled their medical and pharmacological studies in manuscripts. Thus in-patient medical care in the sense of what we today consider a hospital, was an invention driven by Christian mercy and Byzantine innovation.[12] Byzantine hospital staff included the Chief Physician (archiatroi), professional nurses (hypourgoi) and orderlies (hyperetai). By the twelfth century, Constantinople had two well-organized hospitals, staffed by doctors who were both male and female. Facilities included systematic treatment procedures and specialized wards for various diseases.[13]

Medieval hospitals in Europe followed a similar pattern to the Byzantine. They were religious communities, with care provided by monks and nuns. (An old French term for hospital is hôtel-Dieu, "hostel of God.") Some were attached to monasteries; others were independent and had their own endowments, usually of property, which provided income for their support. Some hospitals were multi-functional while others were founded for specific purposes such as leper hospitals, or as refuges for the poor, or for pilgrims: not all cared for the sick.

When and where the first hospital was established is a matter of dispute. According to some authorities (e.g. Ratzinger, p. 141), St. Zoticus built one at Constantinople during the reign of Constantine, but this has been denied (cf. Uhlhorn, I, 319). But that the Christians in the East had founded hospitals before Julian the Apostate came to the throne (361) is evident from the letter which that emperor sent to Arsacius, high-priest of Galatia, directing him to establish a xenodochium in each city to be supported out of the public revenues (Soxomen, V, 16). As he plainly declares, his motive was to rival the philanthropic work of the Christians who cared for the pagans as well as for their own. A splendid instance of this comprehensive charity is found in the work of St. Ephraem who, during the plague at Edessa (375), provided 300 beds for the sufferers. But the most famous foundation was that of St. Basil at Cæsarea in Cappadocia (369). This "Basilias", as it was called, took on the dimensions of a city with its regular streets, buildings for different classes of patients, dwellings for physicians and nurses, workshop and industrial schools. St. Gregory of Nazianzus was deeply impressed by the extent and efficiency of this institution which he calls "an easy ascent to heaven" and which he describes enthusiastically (Or. 39, "In laudem Basilii"; Or. fun. "In Basil.", P.G., XXXVI, 578-579).

https://en.wikipedia.org/wiki/History_of_nursing