It depends on the period, however I'm going to answer specifically for the epidemics of plague in the 1300's as this is the period most people talk about when talking about the bubonic plague. Because what is known as the 'Columbian exchange' had not happened yet, all cases of plague in the 1300's happened in Europe, Asia, and Africa. The most deadly outbreaks tended to be focused around trade routes, and possibly because of climate the worst outbreaks were in Eurasia, and particularly in Europe and Western Asia. In fact it is thought that The Black Death (the outbreak of plague in the 14th century) began in Mongol held areas in Asia, but didn't produce the kind of mass death we think about in terms of plague until it reached Western Europe by way of Italy .At other times plague outbreaks have focused in other areas. After the Columbian exchange plague was among, though not the most deadly of, diseases which hit the Native American populations. Earlier than the Black Death, from about 500 to 700 AD plague struck Turkey and the Mediterranean region and in the early 20th century it was particularly present in China.

https://www.nationalgeographic.com/science/health-and-human-body/human-diseases/the-plague/