An Overview of Hepatitis C

Hepatitis C is an infectious disease of the liver caused by the hepatitis C virus (HCV). It is typically spread through contact with infected blood, but can also be transmitted through sexual contact or passed from mother to child during pregnancy.

Hepatitis C is a slowly progressive disease that can range in severity from a mild, flu-like illness lasting a few weeks to a serious, life-long condition that can severely damage the liver.

In as many as one in five cases, the virus will spontaneously clear soon after infection, showing no detectable signs of virus in the blood. In those whom the virus remains, there are often few, if any, signs of the illness for years—even decades—following initial infection. Some infections, in fact, never progress.

However, in between 10 to 30 percent of cases, hepatitis C can advance to a condition called cirrhosis in which the liver is so extensively damaged as to reduce its ability to function properly.

This can progress to a stage called decompensated cirrhosis wherein the liver is essentially non-functional.

Hepatocellular carcinoma (a type of liver cancer) is also commonly seen in advanced cases of hepatitis C, with rates running as high as 17 times that of the general population.

Types of Hepatitis C Virus

Since the time of its discovery in the 1980s, scientists have been able to identify at least 11 different genetic variations of HCV, called genotypes. The six major HCV genotypes are distributed unevenly throughout the world, with some types predominating within specific geographic regions.

In the United States, HCV genotype 1 accounts for nearly 80 percent of all infections, followed by genotypes 2 and 3. By contrast, genotype 4 is the predominant type in Africa and the Middle East, while genotypes 5 and 6 are most frequently seen in southern Africa and Asia, respectively.

The identification of genotype is important in not only predicting the course of the disease, but in determining which drugs will work best in fighting a particular viral type.

Stages of Hepatitis C Infection

The course of an HCV infection is highly unpredictable since the virus can spontaneously clear in some people, become a persistent infection in others, and advance to serious illness in others still. The stages of infection are also highly variable and are typically defined as being either acute, chronic, or end stage.

An acute infection is one that occurs soon after exposure and is characterized by the rapid onset of symptoms. In the case of hepatitis C, symptoms are almost entirely "silent," with only a handful of individuals likely to experience mild, flu-like illness (generally within two to eight weeks of exposure).

During an acute infection, HCV will primarily target liver cells called hepatocytes. As the virus rapidly replicates—generating upwards of a trillion copies of itself per day—it can cause damage to the liver by directly killing hepatocytes and by stimulating the immune system to produce disease-fighting agents called lymphocytes, which also kill the infected cells.

In anywhere from 20 to 25 percent of cases, HCV will spontaneously clear within the space of six months. In those that don’t, HCV will persist and advance to what is known as a chronic infection.

During a chronic infection, the activation of the immune system triggers an inflammatory response, which stimulates the production of collagen and other substances. These substances, meant to strengthen the architectural of the liver, gradually build ups faster than the body can break them down. Over time, the process causes the accumulation of scar tissue, leading to the development of cirrhosis in about 10 to 15 percent of chronically infected individuals.

End stage hepatitis C is roughly defined as the stage of disease where the risk of mortality is increased due to liver failure, liver cancer, or non-liver-related complications such as kidney failure. Decompensated cirrhosis and hepatocellular carcinoma are the two most common end stage conditions associated with HCV infection. Outcomes for both are generally poor, carrying a five-year survival rate of 50 percent and 30 percent, respectively.

A liver transplant is considered the only effective option for patients with end stage liver disease, although HCV is known to recur in around 80 percent of cases.

Diagnosis and Treatment of Hepatitis C

Hepatitis C infections are confirmed by a simple blood test that detects defensive proteins, called antibodies, specific to the virus. On average, it takes six to eight weeks for the body to produce enough antibodies for a test to be considered accurate. In addition to standard point of care tests, rapid tests are now available, which can deliver results in as little as 30 minutes.

Hepatitis C testing is currently recommended for all adults at high risk of infection, as well as any person born between the years of 1945 and 1965.

Treatment of hepatitis C is generally recommended when a person shows signs of liver inflammation. The course and duration of therapy is determined by the genotype of a person’s virus, as well as the diagnosed stage of infection.

Recent advances in hepatitis C therapy have been nothing short of astonishing, particularly when you consider that HCV was only officially identified in 1989. Today, newer direct acting antivirals (DAAs) are not only less toxic and require shorter treatment duration, they are affecting cure rates of as high as 99 percent in some groups.

However, unlike hepatitis A or hepatitis B, there is still no vaccine to prevent hepatitis C infection.

National and Global Hepatitis C Statistics

Globally, between 150 to 200 million people are chronically infected with hepatitis C, or nearly three percent of the world’s population. The highest concentration of infections is seen in North Africa, the Middle East, and Central and East Asia.

While injecting drug use remains a primary route of infection in developed countries, unsterilized medical procedures—particularly unsafe injections—are considered among the leading cause of hepatitis C in the developing world.

In the United States, hepatitis C is today the most common blood-borne infection, impacting around 3.2 million Americans (or roughly 1.5 percent of the adult population). Injecting drug use accounts for around 80 percent of all cases, followed by sexual contact (10 percent), mother-to-child transmission (4 percent), and needle stick injury (2 percent).

Roughly three in four Americans living with hepatitis C today were born between 1945 and 1965, due largely to tainted blood transfusions. Advances in screening techniques have reduced such risk to less than one out of every two million transfusions.

While the annual U.S. infection rate has stabilized to around 17,000 cases per year, the number of deaths has increased, overtaking HIV/AIDS as a leading cause of death among adults.

Worldwide, hepatitis C causes more death each year than HIV and tuberculosis combined.

Sources:

American Association for the Study of Liver Disease (AASLD). Assessing the Global and Regional Burden of Liver Disease. Washington, D.C.; press release issued November 3, 2013.

Holmberg S, Ly K, Xing J, et al. The Growing Burden of Mortality Associated with Viral Hepatitis in the United States, 1999-2007. 62nd Annual Meeting of the American Association for the Study of Liver Disease (AASLD 2011); San Francisco; November 4-8, 2011, abstract 243.

National Institutes of Health. Hepatitis C Virus Infection. Rockville, Maryland; last updated Oct. 28, 2014.

U.S. Preventive Services Task Force. Final Update Summary: Hepatitis C Screening. Rockville, Maryland; published June 2013.

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