Viral Hepatitis

Hepatitis means inflammation of the liver. The liver is a vital organ that processes nutrients, filters the blood, and fights infections. When the liver is inflamed or damaged, its function can be affected. Heavy alcohol use, toxins, some medications, and certain medical conditions can cause hepatitis. However, hepatitis is often caused by a virus. In the United States, the most common types of viral hepatitis are hepatitis A, hepatitis B, and hepatitis C.

Viral hepatitis is an infection that causes liver inflammation and damage. Inflammation is swelling that occurs when tissues of the body become injured or infected. Inflammation can damage organs. Researchers have discovered several different viruses NIH external link that cause hepatitis, including hepatitis A, B, C, D, and E.

Hepatitis A and hepatitis E typically spread through contact with food or water that has been contaminated by an infected person’s stool. People may also get hepatitis E by eating undercooked pork, deer, or shellfish.

Hepatitis B, hepatitis C, and hepatitis D spread through contact with an infected person’s blood. Hepatitis B and D may also spread through contact with other body fluids. This contact can occur in many ways, including sharing drug needles or having unprotected sex.

The hepatitis A and E viruses typically cause only acute, or short-term, infections. In an acute infection, your body is able to fight off the infection and the virus goes away.

The hepatitis B, C, and D viruses can cause acute and chronic, or long-lasting, infections. Chronic hepatitis occurs when your body isn’t able to fight off the hepatitis virus and the virus does not go away. Chronic hepatitis can lead to complications such as cirrhosis, liver failure, and liver cancer NIH external link. Early diagnosis and treatment of chronic hepatitis can prevent or lower your chances of developing these complications.

When doctors can’t find the cause of a person’s hepatitis, they may call this condition non-A–E hepatitis or hepatitis X. Experts think that unknown viruses other than hepatitis A, B, C, D, and E may cause some cases of hepatitis. Researchers are working to identify these viruses.

Although non-A–E hepatitis is most often acute, it can become chronic.

Hepatitis viruses replicate (multiply) primarily in the liver cells. This can cause the liver to be unable to perform its functions. The following is a list of major functions of the liver:

• The liver helps purify the blood by changing harmful chemicals into harmless ones. The source of these chemicals can be external, such as medications or alcohol, or internal, such as ammonia or bilirubin. Typically, these harmful chemicals are broken down into smaller chemicals or attached to other chemicals that then are eliminated from the body in the urine or stool.
• The liver produces many important substances, especially proteins that are necessary for good health. For example, it produces albumin, the protein building block of the body, as well as the proteins that cause blood to clot properly.
• The liver stores many sugars, fats and vitamins until they are needed elsewhere in the body.
• The liver builds smaller chemicals into larger, more complicated chemicals that are needed elsewhere in the body. Examples of this type of function are the manufacture of a fat, cholesterol, and the protein bilirubin.

When the liver is inflamed, it does not perform these functions well, which brings about many of the symptoms, signs, and problems associated with any type of hepatitis. Each hepatitis viral type (A-F) has both articles and books describing the details of infection with that specific virus. This article is designed to give the reader an overview of the predominant viruses that cause viral hepatitis, their symptoms, diagnosis, and treatments, and should help the reader choose the subject(s) for more in-depth information.

What are the common types of viral hepatitis?

Although the most common types of viral hepatitis are HAV, HBV and HCV, some clinicians had previously considered the acute and chronic phases of hepatic infections as "types" of viral hepatitis. HAV was considered to be acute viral hepatitis because the HAV infections seldom caused permanent liver damage that led to hepatic (liver) failure. HBV and HCV produced chronic viral hepatitis. However, these terms are outdated and not currently used as frequently because all of the viruses that cause hepatitis may have acute phase symptoms (see symptoms below). Prevention techniques and vaccinations have markedly reduced the current incidence of common viral hepatitis infections; however, there remains a population of about 1 to 2 million people in the U.S. with chronic HBV, and about 3.5 million with chronic HCV according to the CDC. Statistics are incomplete for determining how many new infections occur each year; the CDC documented infections but then goes on to estimate the actual numbers by further estimating the number of unreported infections (see following sections and reference 1).

Hepatitis A (HAV)

In 2016, there were 2,007 new HAV cases reported to the CDC. The hepatitis caused by HAV is an acute illness (acute viral hepatitis) that never becomes chronic. At one time, hepatitis A was referred to as "infectious hepatitis" because it could be spread easily from person to person like other viral infections. Infection with hepatitis A virus can be spread through the ingestion of food or water, especially where unsanitary conditions allow water or food to become contaminated by human waste containing hepatitis A (the fecal-oral mode of transmission). Hepatitis A typically is spread among household members and close contacts through the passage of oral secretions (intimate kissing) or stool (poor hand washing). It also is common to have infection spread to customers in restaurants and among children and workers in day care centers if hand washing and sanitary precautions are not observed.

Hepatitis B (HBV)

There were 3,218 new cases of HBV infection estimated by the CDC in 2016 and more than 1,698 people died due to the consequences of chronic hepatitis B infection in the United States according to the CDC. HBV hepatitis was at one time referred to as "serum hepatitis," because it was thought that the only way HBV could spread was through blood or serum (the liquid portion of blood) containing the virus. It is now known that HBV can spread by sexual contact, the transfer of blood or serum through shared needles in drug abusers, accidental needle sticks with needles contaminated with infected blood, blood transfusions, hemodialysis, and by infected mothers to their newborns. The infection also can be spread by tattooing, body piercing, and sharing razors and toothbrushes (if there is contamination with infected blood). About 5% to 10% of patients with HBV hepatitis develop chronic HBV infection (infection lasting at least six months and often years to decades) and can infect others as long as they remain infected. Patients with chronic HBV infection also are at risk of developing cirrhosis, liver failure, and liver cancer. It is estimated that there are 2.2 million people in the U.S. and 2 billion people worldwide who suffer with chronic HBV infections.

Hepatitis C (HCV)

The CDC reported that there were 2,967 reported new cases of hepatitis C in 2016. The CDC reports that the actual number of acute cases are estimated to be 13.9 times the number of reported cases in any year, thus, it is estimated that there were actually 41,200 acute hepatitis C cases occurring in 2016. HCV hepatitis was previously referred to as "non-A, non-B hepatitis," because the causative virus had not been identified, but it was known to be neither HAV nor HBV. HCV usually is spread by shared needles among drug abusers, blood transfusion, hemodialysis, and needle sticks. Approximately 75%-90% of transfusion-associated hepatitis is caused by HCV. Transmission of the virus by sexual contact has been reported, but is considered rare. An estimated 75% to 85% of patients with acute HCV infection develop chronic infection. Patients with chronic HCV infection can continue to infect others. Patients with chronic HCV infection are at risk for developing cirrhosis, liver failure, and liver cancer. It is estimated that there are about 3.5 million people with chronic HCV infection in the U.S.

Types D, E, and G Hepatitis

There also are viral hepatitis types D, E, and G. The most important of these at present is the hepatitis D virus (HDV), also known as the delta virus or agent. It is a small virus that requires concomitant infection with HBV to survive. HDV cannot survive on its own because it requires a protein that the HBV makes (the envelope protein, also called surface antigen) to enable it to infect liver cells. The ways in which HDV is spread are by shared needles among drug abusers, contaminated blood, and by sexual contact; essentially the same ways as HBV.

Individuals who already have chronic HBV infection can acquire HDV infection at the same time as they acquire the HBV infection, or at a later time. Those with chronic hepatitis due to HBV and HDV develop cirrhosis (severe liver scarring) rapidly. Moreover, the combination of HDV and HBV virus infection is very difficult to treat.

Hepatitis E virus (HEV) is similar to HAV in terms of disease, and mainly occurs in Asia where it is transmitted by contaminated water.

Hepatitis G virus (HGV, also termed GBV-C) was recently discovered and resembles HCV, but more closely, the flaviviruses. The virus and its effects are under investigation, and its role in causing disease in humans is unclear.

Who is at risk for viral hepatitis?

People who are most at risk for developing viral hepatitis are:

• Workers in the health care professions
• Asians and Pacific Islanders
• Sewage and water treatment workers
• People with multiple sexual partners
• Intravenous drug users
• HIV patients
• People with hemophilia who receive blood clotting factors

Blood transfusion, once a common means of spreading viral hepatitis, now is a rare cause of hepatitis. Viral hepatitis is generally thought to be as much as 10 times more common among lower socioeconomic and poorly educated individuals. About one third of all cases of hepatitis come from an unknown or unidentifiable source. This means that a person does not have to be in a high-risk group in order to be infected with a hepatitis virus. In countries with poor sanitation, food and water contamination with HAV increases risk. Some day care centers may become contaminated with HAV, so children at such centers are at a higher risk for HAV infections.