On page 332 there is the mention of the 7th century plagues can refer to theplagues that struch Europe in about 1347and just moved to China, exp. in real time history it was the 8th century not the 7th.

TheBlack Death and the Bubonic plague where both part of these time period plagues.

The rest is some info found on the plagues the information was gathered from Wikipedia and Wkipedia.

The Black Death, or the Black Plague, was one of the most deadly pandemics in human history, widely thought to have been caused by a bacterium named Yersinia pestis.[1] It probably began in Central Asia[2] and spread to Europe by the late 1340s.[3] The total number of deaths worldwide from the pandemic is estimated at 75 million people;[4] there were an estimated 25-50 million deaths in Europe.[5][6][7] The Black Death is estimated to have killed 30% to 60% of Europe's population.[8][9][10] It may have reduced the world's population from an estimated 450 million to between 350 and 375 million in 1400.[11]

and


The bubonic plague or bubonic fever is the best-known variant of the deadly infectious disease caused by the enterobacteria Yersinia pestis (Pasteurella pestis). The epidemiological use of the term plague is currently applied to bacterial infections that cause buboes, although historically the medical use of the term plague has been applied to pandemic infections in general.