In an effort to circumvent the hold the Ottoman Empire held on the overland trade routes to East Asia and the hold that the Aeterni regis granted to Portugal on maritime routes via the African coast and the Indian Ocean, of the nascent Spanish Empire decided to fund Columbus' voyage in 1492, which eventually led to the establishment of settler-colonial states and the migration of millions of Europeans to the Americas. The population of African and European peoples in the Americas grew steadily starting in 1492, while at the same time the indigenous population began to plummet. Eurasian diseases such as influenza, pneumonic plagues, and smallpox devastated the Native Americans, who did not have immunity to them. Conflict and outright warfare with Western European newcomers and other American tribes further reduced populations and disrupted traditional societies. The extent and causes of decline have been characterized as genocide.