A disease that developed and killed within a few days decimates Europe and changes the course of history.

How can we cope with this tricky virus now rampant worldwide? The key to this battle lies in our immune system. Using high-tech microscopes, we examine how our immune systems fight these pathogens to understand the efficacy of potential treatments.

Every person is playing host to at least 40 trillion non-human microorganisms. Collectively, these microbes constitute what's called our microbiome. New science is revealing what these microbes do for us. How can understanding this, help us live healthier lives?

Author David Quammen predicted the coronavirus pandemic nearly a decade ago, in his best-selling book "Spillover." Now, he shows us how the same remote Montana lab that spawned his work, is on the front-lines of efforts to combat Covid-19.

How safe are we from the next pandemic? Journey to the island of Riems, off the coast of Germany on the Baltic Sea, to the “Alcatraz for viruses,” where a collective of highly specialized experts from around the world work tirelessly to combat the growing virus threat.