between the 520s and 540s, possibly in southeast Africa, around the ivory markets of what is now Zanzibar, the disease mutated into a super-lethal strain. It then met with environmental conditions ripe for easy infection—the climate crisis of 536 contributed to this by weakening human and rat populations and forcing them into closer-than-usual cohabitation.42 And it spread rapidly along the long-established and booming trade networks around the Mediterranean.
