In the 10 years since the drugmaker Gilead debuted a revolutionary treatment for hepatitis C, a wave of new therapies have been used to cure millions of people around the world of the blood-borne virus.

Today, 15 countries, including Egypt, Canada and Australia, are on track to eliminate hepatitis C during this decade, according to the Center for Disease Analysis Foundation, a nonprofit. Each has pursued a dogged national screening and treatment campaign.