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How Viruses Cause Disease

Introductory virology course that covers the interplay between viruses and their host organisms, with with the goal of understanding viral diseases and their prevention.


Course at a Glance

About the Course

This introductory virology course explores the interplay between viruses and their host organisms. The course begins with an overview of how infection is established in a host, then moves to a virologist's view of immune defenses.  Next we consider how the replication strategy and the host response determine the outcome of infection, such that some are short and others are of long duration. The mechanisms by which virus infections transform cells in culture are explored, a process that may lead to tumor formation in animals. We then move to a discussion of how viral infections are controlled by vaccines and antiviral drugs. After an introduction to viral evolution, we discuss the principles learned from zoonotic infections, emerging infections, and humankind's experiences with epidemic and pandemic viral infections. The course ends with an exploration of unusual infectious agents such as viroids, satellites, and prions, followed by a discussion of the causative agent of the most serious current worldwide epidemic, HIV-1.

Course Syllabus

Week 1
Infection basics
Entry into the host
Viral spread
Tissue invasion and tropism
Transmission and seasonality
Week 2
Innate immune responses
Sentinels and complement
Adaptive immunity
Week 3
Viral virulence
Mechanisms of cell injury I
Mechanisms of cell injury II
Host susceptibility
Week 4
Acute infections
West Nile fever
Week 5
Persistent infections
Persistence by modulating the adaptive response
Two persistent infections
Herpes simplex virus
Epstein-Barr virus
Week 6
RNA tumor viruses
Transforming retroviruses
DNA tumor viruses
Epiphenomena of a unique life style
Week 7
How do you make a vaccine?
Inactivated vaccines
Attenuated vaccines
Week 8
Antiviral discovery
Antiviral resistance
Other antiviral targets
HIV antivirals
Week 9
Viral evolution
Drivers of evolution
Error threshold and bottlenecks
Origins of viruses
Week 10
Emerging viruses
Host-virus interactions
Examples of emerging viruses
Canine parvovirus
Week 11
Transmissible spongiform encephalopathies
Week 12
The origin of HIV
HIV pathogenesis
An amazing but deadly virus

Recommended Background

Two semesters of a rigorous, molecularly-oriented introductory biology course and Virology I: How Viruses Work.

Suggested Readings

The recommended textbook is Principles of Virology. Vol I: Molecular Biology, Vol. II: Pathogenesis and Control (S.J. Flint et al., Third Edition, ASM Press 2009). You don't need to buy this book to do well in this course, as the lectures are self-contained, but if you are very interested in virology, it's a great resource.

Students are expected to read Prof. Racaniello’s virology blog ( which will contain information relevant to the course.

Students are expected to listen to the weekly podcast This Week in Virolog produced by Prof. Racaniello, for additional material about viruses relevant to the course. You can subscribe to TWiV at or on  iTunes

Course Format

This class consists of lecture videos which are between 10-15 minutes in length. There will also be standalone quizzes and a final exam.


  • Will I get a Statement of Accomplishment after completing this class?

    Yes. Students who successfully complete the class will receive a Statement of Accomplishment.

  • What resources will I need for this class?

    For this course, you need an Internet connection and the time to read, write, discuss, and enjoy the various resources on virology.