Research from 2017 suggests plague first infected humans in Europe and Asia in the Late Neolithic-Early Bronze Age.[33] Research in 2018 found evidence of Yersinia pestis in an ancient Swedish tomb, which may have been associated with the "Neolithic decline" around 3000 BCE, in which European populations fell significantly.[34][35] This Y. pestis may have been different from more modern types, with bubonic plague transmissible by fleas first known from Bronze Age remains near Samara.[36]
The symptoms of bubonic plague are first attested in a fragment of Rufus of Ephesus preserved by Oribasius; these ancient medical authorities suggest bubonic plague had appeared in the Roman Empire before the reign of Trajan, six centuries before arriving at Pelusium in the reign of Justinian I.[37] In 2013, researchers confirmed earlier speculation that the cause of the Plague of Justinian (541–549 CE, with recurrences until 750) was Y. pestis.[38][39] This is known as the first plague pandemic. In 610, the Chinese physician Chao Yuanfang described a "malignant bubo" "coming in abruptly with high fever together with the appearance of a bundle of nodes beneath the tissue."[40] The Chinese physician Sun Simo who died in 652 also mentioned a "malignant bubo" and plague that was common in Lingnan (Guangzhou). Ole Jørgen Benedictow believes that this indicates it was an offshoot of the first plague pandemic which made its way eastward to Chinese territory by around 600.[41]
