Updated December 29, 2014.

The Disease

Hepatitis C is a disease of the liver caused by the hepatitis C virus (HCV). Before the late 1980s, physicians only knew this disease as "non-A, non-B hepatitis" because laboratory tests to identify HCV hadn't been developed. Now, at least six different variations of the hepatitis C virus are recognized. These different types, called genotypes, are basically genetic variations on the same theme that can lead to hepatitis C infection.

Though each genotype is diagnosed as hepatitis C infection, it is important to know which one you have because certain genotypes are more challenging to treat.

• The Different Types of Hepatitis C
• The Basics of Hepatitis

About four million people in the United States have been infected with HCV. Since about 25% of those have cleared the virus, around 3 million people are carriers of HCV and can spread the virus to others. Worldwide, about 170 million people are infected.

Acute Hepatitis C

For the most part, hepatitis C is not detected in the acute phase since the symptoms are silent or mild (unlike hepatitis A in which the acute phase can be quite dramatic) and liver failure is rare. There are rare occasions when people have a mild flu-like syndrome, or other symptoms, that prompt testing but usually hepatitis C infection is only picked up by screening people believed to be at risk.
Hepatitis C begins relatively suddenly (acutely) after an average incubation period of 7 weeks. This period, which is the time between exposure to HCV and developing signs and symptoms, could be as short as about 2 weeks, but as long as 23 weeks.

Once your body is exposed to HCV, the virus travels in your blood to the liver. As a hepatotrophic virus (viruses such as hepatitis A, B, and E that have a strong affinity for infecting the liver), HCV feels right at home in the liver cell, called a hepatocyte. When enough hepatocytes are infected, your immune system will respond by sending to the liver specialized virus-fighting cells, called lymphocytes. This immune response causes liver inflammation, also known as hepatitis.

Inflammation is a double-edged sword. On one hand it is necessary because it means that your immune system is doing its job and is trying to rid the hepatocytes of the virus. However, on the other hand, too much inflammation for too long creates damage. If the immune system can't get rid of the virus in about six months, by definition you've developed chronic hepatitis C.

Chronic Viral Hepatitis C

Hepatitis C is really considered to be a chronic disease. It develops in as many as 80% of people with acute infection and is defined as being unable to clear the virus within six months. As your immune system keeps trying to attack HCV, the liver actually becomes damaged by the chronic inflammation, which often results in fibrosis. Excessive fibrosis in the liver is called cirrhosis. Since cirrhosis is not reversible, most doctors suggest early treatment to prevent as much cirrhosis from developing as possible.
Because so many patients with viral hepatitis are asymptomatic (having no symptoms), many people have chronic hepatitis but don't realize they're infected. It's very common for people to learn of their infection after donating blood or from other unrelated lab tests.

• Ten Complications of Hepatitis
• Can a Doctor Diagnose Cirrhosis Without a Biopsy?
• Should I Eat a Special Diet if I Have Cirrhosis?

Symptoms

The symptoms of viral hepatitis are very generalized, and in the early stages of infection usually resemble a case of the flu. However, most infected people (up to 70%) will not show any symptoms at all and are said to be asymptomatic.
For those who do have symptoms, typically they first experience tiredness, joint and muscle pain, loss of appetite, nausea and diarrhea. While jaundice is a very well-known sign of hepatitis, many people never experience it! For those who do, some might notice dark-colored urine or clay-colored stools up to five days before jaundice develops. In most cases, all these symptoms go away on their own. For people who develop chronic hepatitis C, extreme tiredness (fatigue) is a common complaint.

• More About Hepatitis Symptoms
• Four Important Common Hepatitis Symptoms

Transmission

The hepatitis C virus is spread through direct contact with infected blood. About half of new hepatitis C cases are spread by injection drug use. In the past (before 1992), people who received blood transfusions and organ transplants were at high risk for exposure to HCV. However, today, blood lab technicians are able to carefully screen for hepatitis C so transfusions and transplants are no longer a high risk for hepatitis C exposure and transmission.

• Can I Catch Hepatitis C By Drinking After Someone?
• Can I Spread Hepatitis C To My Baby?

Diagnosis

Doctors diagnose viral hepatitis C by looking for antibodies to the virus using a blood test called an EIA, or enzyme immunoassay. The test is very sensitive, but not very selective in looking for antibodies, so a positive EIA might not be correct. Depending on your risk factors, doctors check the test result by using another test, called a RIBA (recombinant immunoblot assay). A positive RIBA confirms a hepatitis C diagnosis.
Since testing for antibodies alone cannot determine if the infection is acute, chronic, or a past infection that the body has cleared, doctors must use several different tests along with signs and symptoms to determine your diagnosis.

• More About Diagnosing Hepatitis