The Centers for Disease Control and Prevention is now advising people to get screened for hepatitis B at least once in their lives. Though the infection can be managed with antivirals and prevented with a highly effective childhood vaccine, many Americans today are still living with chronic hepatitis B, which can raise the risk of liver damage and cancer. Two-thirds of these Americans may not even know they have the disease, according to the CDC.

Hepatitis B is one of several unrelated viruses that are the primary cause of hepatitis (liver inflammation) in people. It spreads through blood and other bodily fluids, which can be transmitted through sex, sharing contaminated needles and syringes, or from mother to child in the womb. Most people initially infected with hepatitis B won’t have symptoms, but those who do experience fatigue, poor appetite, stomach pain, nausea, and jaundice. The infection is often short-lasting, but sometimes the virus lingers in the body. Untreated chronic hepatitis B can damage the liver over time, increasing the odds of developing cirrhosis and liver cancer.

The first vaccine for hepatitis B was introduced worldwide in the early 1980s, and childhood vaccination became routine in the U.S. starting in the early 1990s. The vaccine is highly effective at preventing hepatitis B, and following its introduction the rate of new cases steadily dropped in the U.S. But more recently, the incidence of hepatitis B has stayed stable, if low. And though U.S.-born children are widely protected from it, there are many residents born in countries where vaccination is less common, as well as older adults who may have never gotten vaccinated at all (the CDC recommends that people as old as 59 should get the vaccine).

The new advice released Thursday is an update to the CDC’s guidelines previously published in 2008. These called for people at higher risk for infection to be screened for the virus, such as those born in countries where it’s common, people who currently or used to inject recreational drugs, and men who have sex with men. But the CDC now says that everyone over the age of 18 should get tested for the virus at least once in their lifetime.

Today, an estimated 20,000 new cases of hepatitis B occur in the U.S., according to the CDC. About a half-million to 2.4 million Americans are living with chronic hepatitis B, and up to two-thirds might be unaware of their infection. About 1,600 U.S. deaths attributed to hepatitis B were documented in 2019, though it’s likely that this is an undercount.

Though most people don’t have hepatitis B, the CDC says that one-time universal screening should still be cost-effective overall and life-saving. Based on a recent analysis cited by the agency, the change would be expected to prevent roughly two liver transplants and 10 hepatitis B-related deaths per every 100,000 Americans screened, along with many cases of cirrhosis.

The guidelines are also meant to bolster an ambitious goal by the World Health Organization to effectively eliminate viral hepatitis everywhere by 2030. Globally, according to the WHO, 296 million people were living with chronic hepatitis B in 2019, while 1.5 million people are becoming newly infected each year. These infections are estimated to kill more than 800,000 people a year, mostly from liver cancer and cirrhosis.

There is no cure for chronic hepatitis B, but antiviral treatments can keep it in check. Newborns who contract the virus can also be given treatment to help prevent chronic infection.