Population history of indigenous peoples of the Americas scope of the epidemics over the years was tremendous, killing millions of people—possibly in excess of 90% of the population in the hardest hit areas—and creating one of "the greatest human catastrophe in history, far exceeding even the disaster of the Black Death of medieval Europe", which had killed up to one-third of the people in Europe and Asia between 1347 and 1351. One of the most devastating diseases was smallpox, but other deadly diseases included typhus, measles, influenza, bubonic plague, cholera, malaria, tuberculosis, mumps, yellow fever and pertussis, which were chronic in Eurasia. This transfer of disease between the
Mexican Americans an army to defend themselves from invading American forces after the Mexican army retreated from Alta California to defend other parts of Mexico. The Californios defeated an American force in Los Angeles on September 30, 1846. In turn, they were defeated after the Americans reinforced their forces in what is now southern California. Tens of thousands of miners and associated people arrived during the California Gold Rush, and their activities in some areas meant the end of the Californios' ranching lifestyle. Many of the English-speaking 49ers turned from mining to farming and moved, often illegally, onto land granted to Californios