Short answers, pulled from the story.
The Plague of Cyprian began around Easter of 249 AD and lasted until about 262, possibly extending to 270. Historians debate the exact start date and geographical origin of this disease.
Cyprian wrote that victims suffered from fever, continuous vomiting, deafness, blindness, diarrhea, swollen throats, and conjunctivital bleeding where blood filled the eyes. Victims also experienced paralysis of the legs and feet which often led to amputation due to diseased putrefaction.
At the height of the outbreak, 5,000 people a day were said to be dying in Rome. One historian calculated that the population of Alexandria dropped from 500,000 to 190,000 during the plague years.
Emperor Claudius II Gothicus died in 270 during an incident involving Scythian armies plundering Crete and Cyprus being stricken with pestilence. Scholars remain unsure if his death resulted from the same plague or a new outbreak.
Christianity gained converts because the Church promised an afterlife and clergy helped the sick and poor while others fled. The threat of imminent death combined with conviction among clergy won many followers who found hope in eternal life.