CDC Recommends Hepatitis C Testing for All Baby Boomers

Jon is a staff writer for Science.

On top of rock 'n' roll, drugs, sexual liberation, and shaggy hair, the baby boomers can also lay claim to the hepatitis C virus (HCV) as a defining feature of their generation. A report issued by the U.S. Centers for Disease Control and Prevention (CDC) today recommends that all Americans born between 1945 and 1965 receive an HCV test.

An estimated 2.7 million to 3.9 million people in the United States are infected with this liver-damaging—and sometimes lethal—virus. CDC calculates that roughly 75% of the infected population comes from the baby boomer generation: 3.25% of people born in that "birth cohort" test positive for HCV, which is five times higher than adults born before 1945 or after 1965. Males are twice as likely to be infected as females, and the prevalence in black males (8.12%) far exceeds that in white (4.05%) and Mexican-American males (3.41%).

"We don't think every [baby boomer] needs to run out and see their primary care provider and get tested immediately, but they shouldn't put this off for years either," says CDC's Bryce Smith, a social scientist who is the lead author of the recommendations published in the Morbidity and Mortality Weekly Report. "The sooner it can happen, the more lives we’ll be able to save."

There are many unknowns about HCV, from its routes of transmission to its epidemiology. HCV wasn't identified until 1988, and the surveillance system for the virus remains far less robust than the one that tracks HIV infection in the country. Still, CDC estimates that during the 1980s, the virus infected an average of 230,000 Americans each year. It mainly spread through contaminated blood and blood products; injecting drug users, transplant recipients, and hemophiliacs were the hardest hit. The virus causes cirrhosis in about 20% of the people infected for longer than 20 years—many need liver transplants to survive—and it's the leading cause of liver cancer in this country. Toxic and expensive drug treatments have cured the infection in a small percentage of infected people, but new, powerful, and safer antivirals have recently come to market that promise to have a much broader impact. There is no HCV vaccine.

Several factors led to a steep drop in cases after 1990, the year an HCV blood test was introduced. The blood test virtually eliminated spread through transfusions and blood products. Injecting drug users also saw declining new infection rates because the virus had "saturated" that population, and because, in the wake of the booming HIV epidemic, many communities began needle and syringe exchange programs to make injection safer. In 2010, the estimated number of new infections in the United States was only 17,000.

As Smith and colleagues explain in the report, studies have shown that 45% to 85% of HCV-infected people in the United States do not know they carry the virus. An estimated 45% of people who learn they are infected report no known risk factor for acquiring HCV. "People just don’t know the various ways they might be able to acquire hepatitis C, and that's really the point of just testing everyone in that [baby boomer] birth cohort," Smith says. "It's worth acknowledging that all of these exposures happened in the '70s and '80s, and memories may not be that good."

HCV can live outside the body for a week—HIV, in contrast, dies within minutes—which means that transmission can readily occur by sharing a toothbrush, razor blade, or a straw to snort drugs. "Hepatitis C is a very hardy virus," Smith notes. Transmission can also occur from infected mother to child and unsterile tattoo needles. Researchers still debate the importance of sexual transmission, although people who report having had more than 20 partners have a 4.5-fold increased risk. "We're not sure if it's due to the sexual behavior itself or if it's a proxy for other behaviors," Smith says.

CDC evaluated several birth cohorts over the past 4 years and determined that universal testing of baby boomers was the most cost-effective strategy for detecting undiagnosed HCV infections in the United States. Models predict that in the absence of improved testing and treatment, over the next 40 to 50 years, nearly 2 million Americans will develop cirrhosis, hepatocellular carcinoma will afflict 400,000 others, and HCV-related complications will kill about 1 million people.

Until 2011, HCV treatment relied on alpha-interferon and ribavirin, drugs that have serious side effects and work by indirect and somewhat fuzzy mechanisms. That year, two protease inhibitors came to market that directly attack the virus, and cure rates have doubled in infected people who have used them. Ongoing clinical trials with 20 other so-called direct-acting antivirals have had even more impressive results against HCV, and researchers have high hopes that curing this devastating disease will become routine—but only if people know they are infected and seek treatment.

*Correction 12:37 p.m., 1 October: The first hepatitis C test was introduced in 1990, not 1992, as previously written.

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