When European explorers and travelers spread out, they brought with them the germs that they had become essentially immune to, that they had learned how to tolerate over hundreds and hundreds of years, thousands of years, of living with domesticated animals who were the sources of those pathogens.
Quando os exploradores e viajantes europeus se espalharam, trouxeram com eles os germes aos quais eles já tinham se tornado essencialmente imunes, que eles tinham aprendido a tolerar por centenas e centenas de anos, milhares de anos, vivendo com animais domesticados que eram as origens desses germes.