US baby boomers have been advised by health officials for the first time to get tested for the liver-destroying virus hepatitis C.
Those born between 1945-1965 are most likely to be infected but it is thought only a quarter of this generation has been tested for the virus.
The US Centers for Disease Control (CDC) believes its campaign could save more than 120,000 lives.
The CDC estimates some 17,000 hepatitis C infections currently occur each year.
Health officials believe hundreds of thousands of infections occurred each year in the 1970s and '80s, when baby boomers would have been young adults.
The disease, which was first identified in 1989, can take decades to cause liver damage. Many of those infected may not even be aware of their condition.
One reason for the CDC advice is that from 1999-2007 the number of Americans dying from hepatitis C-related diseases nearly doubled.
Two million of the 3.2 million Americans known to be infected with the blood-borne virus are baby boomers.
CDC officials believe new testing could lead to 800,000 more baby boomers seeking treatment.
Many infections of hepatitis C come from sharing needles to inject drugs. Before widespread screening began in 1992, it was also transmitted through blood transfusions.
"The CDC views hepatitis C as an unrecognised health crisis for the country, and we believe the time is now for a bold response," said Dr John Ward, the CDC's hepatitis chief.