Chronic hepatitis C infection is caused by the hepatitis C virus (HCV). As the virus enters the body, it causes an infection in the liver. Over time, the infection scars the liver and prevents it from working normally. This condition can be fatal if not treated.

According to the Centers for Disease Control and Prevention (CDC), more than 3.5 million Americans are estimated to have hepatitis C. Many of them don’t know they have it. There’s a vaccine for hepatitis A and hepatitis B, but no vaccine for hepatitis C.

Acute and chronic hepatitis C are caused by the same virus. Acute hepatitis C develops after initial infection. This stage can last up to six months. Many people have no symptoms during the acute stage and never find out that they’re infected.

About 80 percent of people with acute hepatitis C develop chronic hepatitis C, according to the CDC. Of that 80 percent, up to 90 percent will develop severe liver damage. Another 20 percent will develop cirrhosis (severe scarring of the liver).

Chronic hepatitis C is often difficult to diagnose because most people have no early symptoms. Only about 25 percent of people experience symptoms when they first contract the virus. Symptoms can include:

Most symptoms of chronic hepatitis C don’t appear until cirrhosis develops and the liver begins to fail. Symptoms can include:

Fluid can sometimes collect in the abdomen. Jaundice (yellowing of the skin) only appears in people with advanced cirrhosis.

Most people who contract hepatitis C get it from infected blood. People who are infected can pass on the virus to others by sharing needles and syringes. Hepatitis C spreads easily among intravenous drug users. It’s also possible to be infected by sharing a razor.

You may also become infected by a toothbrush if you share one while your gums are bleeding. However, the risk of infection from a shared toothbrush is much lower. Although transmission from sexual contact with an infected person is possible, it’s rare.

The only way to confirm a hepatitis C infection is through a blood test. The most common test is an HCV antibody test. A positive result means you’ve been exposed to the virus, but you may not be infected. To confirm infection, you must undergo an HCV viral load test to check for genetic material (RNA). This can confirm whether you are carrying the virus in your body.

Your doctor can also order a third test to check what type of hepatitis C virus you have. There are six different genotypes of hepatitis C. Treatment for each kind is slightly different.

The most common treatment for chronic hepatitis C is a combination of highly active antiviral agents known as direct-acting antivirals (DAAs). These new medications target specific components in the HCV replication cycle, preventing further infection and leading to viral clearance. You may need to take these drugs anywhere from 8 weeks to 24 weeks, depending on the health of your liver and your exposure to prior treatments for HCV infection.

Side effects are rare, but may include:

According to a study published in Gastroenterology, approximately 45 percent of all liver transplants in the United States are done on people with chronic hepatitis C infection that has progressed to cirrhosis. People with an active HCV infection will remain infected even after receiving a liver transplant. However, with the introduction of DAAs, there are many options for treatment and cure of HCV infection after receiving a transplant.

The best thing you can do to protect your liver from hepatitis C is to get an early diagnosis. The earlier you start medication, the higher your chances are for preventing liver failure.

People with chronic hepatitis C shouldn’t drink alcohol. They should maintain a healthy weight and avoid excessive fat in their diets.

After you have finished taking medication, you should still have your liver enzymes checked regularly to make sure your liver is healthy.