I recently read 'The Monkey and the Fish' by Dave Gibbons and it was worth reading just for this section on Page 100:
Historian Rodney Stark, in his great book, The Rise of Christianity, wonders why the Christian movement grew so rapidly in the first few centuries after Jesus' crucifixion. Its adherents were a small band of social outcasts. What transformed this ragtag groups of zealots into a global movement at such a spectacular pace?
Stark's inquiry concluded that surge in growth of Christianity was rooted in the response of early Christians to a wave of great pandemics. At least two plagues wracked the developing world in the first three centuries after the death of Christ, and Christians did something no one else would do. They stayed. They helped. And many gave their lives in doing so.
In Stark's book, Dionysius, the bishop of Alexandria, described in a letter how believers responded to a deadly plague that killed an estimated five thousand people a day in the Roman Empire sometime around 260AD: "Most of our brother Christians showed unbounded love and loyalty, never sparing themselves and thinking only of one another. Heedless of danger, they took charge of the sick, attending to their every need and ministering to them in Christ., and with them departed this life serenely happy; for they were infected by others with the disease, drawing on themselves the sickness of the neighbours and cheerfully accepting their pains. Many, in nursing and curing others, transferred their death to themselves and died in their stead....The best brothers lost their lives in this way"