From the flu to COVID-19, viruses are a major threat in our everyday lives. In today’s episode of Crash Course Biology, we’ll learn why viruses are like genes in a box, and how they invade and spread between cells. We’ll also discover how vaccines and medicines help our bodies fight back.


Introduction: Discovering Viruses 00:00​
What We Have in Common With Viruses 1:24​
Evolutionary Theories of Viruses 2:49​
Hosts & Infection 3:55​
Retroviruses 6:49​
Vaccines 8:11​
Dr. Quarraisha Abdool Karim & Antivirals 9:41​
Review & Credits 11:39​