Hepatitis C is a virus that's long been viewed as a silent killer. You may go without symptoms for decades, while it gradually destroys your liver. Yet the disease has been making a lot of noise as of late, ever since a true game-changer hit the scene: a cure. The new class of drugs has been widely celebrated. Scientists have rejoiced. Hundreds of thousands of patients have been cured, tens of millions more worldwide stand to benefit.

But the drugs, which have amplified the U.S. debate over drug pricing, also proved there's a huge market for treating a common liver disease. Hepatitis C is the most common bloodborne infection in the United States, and in its first year on the market, the main drug, Sovaldi, ballooned into the second best selling drug in the world. Overall these drugs have become the top selling new products in the history of the industry.

Now, the successes of Hepatitis C appear to be fueling a new race: a cure for the virus' often overlooked, but much more common relative, Hepatitis B.

One only needs to travel a mere 30 miles north of Philadelphia, to a 1960s style beige box of a building hidden off a country road, to understand the ways in which this development is unfolding.