Infection with a virus is a common cause of hepatitis. The five viruses primarily associated with hepatitis are named in the order of their discovery: A, B, C, D, and E. In the United States, acute viral hepatitis is most commonly caused by hepatitis A virus (HAV), hepatitis B virus (HBV), and hepatitis C virus (HCV). Only HBV and HCV infection commonly cause chronic hepatitis.
Hepatitis A (HAV) is highly contagious and is spread through water and food that have been contaminated with the hepatitis A virus. HAV infection rates have steadily declined since 1995, when a vaccine was introduced. In 2014, about 1,200 acute cases of hepatitis A were reported nationwide to the Centers for Disease Control and Prevention (CDC). Actual numbers may have been higher, however, since people with no symptoms or only mild symptoms may not have realized they were infected. The CDC estimates that the number of infections in 2014 was probably closer to 2,500 once corrected for underreporting and asymptomatic infections.
Hepatitis A causes an acute infection but not a chronic form of the disease. Treatment usually involves supportive therapy only, and most people recover fully within about six months. Early in the course of HAV infection, the body develops antibodies to the virus, so after the infection has resolved, a person will have lifelong immunity from the disease.
Hepatitis B (HBV) can be spread by contact with the blood, semen, or another body fluid from an infected person. In North America and Europe, the virus is most often spread by sharing needles, syringes, or other equipment used to inject drugs; through sexual contact; and from mother to child during pregnancy (rarely in the U.S., but commonly in many parts of the world).
Infection with the hepatitis B virus formerly was the most common cause of acute viral hepatitis in the United States, but vaccination has led to gradually decreasing rates. According to the CDC, there were about 19,200 new cases of HBV infection in the United States in 2014. The official number of reported hepatitis B cases is much smaller, however, because many people don't know they are infected and never seek medical attention. HBV infection rates are highest among adults, particularly men aged 25-44.
The likelihood of an acute HBV infection becoming a chronic infection depends largely upon the age at which a person becomes infected. The younger a person is when he or she becomes infected, the more likely the infection will become chronic. About 90% of infants who acquire the disease will develop chronic infections. Conversely, less than 5% of adults who become infected with HBV progress to chronic hepatitis B.
Treatment for acute HBV infection usually involves supportive therapy only, and most people recover fully within about six months. Early in the course of HBV infection, the body develops antibodies to the virus, so after the infection has resolved, a person will have lifelong immunity from the disease.
People who develop chronic hepatitis B often remain free of signs and symptoms of illness for decades. Drug treatment may help slow the development or progression of liver damage caused by chronic infection. Liver transplantation may be performed in cases of liver failure. A current list of approved drugs used to treat hepatitis B can be found by visiting the U.S. Food and Drug Administration web site.
Hepatitis C (HCV) is spread by exposure to contaminated blood. The most common mechanism of exposure to HCV is the sharing of needles used in injecting drugs of abuse such, as cocaine or heroin. Other means of becoming infected include occupational exposure of healthcare workers via used needles or other sharp objects; through sexual activity that results in tissue tears; from mother to baby during childbirth; and through the sharing of personal items contaminated with blood, such as razors and toothbrushes.
In 2014, there were about 30,500 cases of acute hepatitis C in the United States. Many cases are not reported and many people do not know that they have an infection because they have no symptoms. Of those who become infected, about 75-85% develop the chronic form of hepatitis C. According to the CDC, there are an estimated 3.5 million people in the U.S. who have chronic hepatitis C. About 60-70% of people with untreated chronic hepatitis C will develop chronic liver disease. Without treatment, roughly 5-20% will develop cirrhosis over many years, and 1-5% are estimated to die from a condition that results from chronic infection, such as cirrhosis or liver cancer.
There is no vaccine available to prevent hepatitis C, but research is in progress to develop one. Currently, the best way to avoid becoming infected is to limit exposure to possible sources of the virus, especially the sharing of needles to inject drugs. Both acute and chronic HCV can be treated, usually with a combination of drugs (see Treatment below).
Hepatitis D and E are rare in the U.S. Hepatitis D only causes an infection when hepatitis B is present and can make that infection more severe. It is usually spread by exposure to infected blood or needles. Hepatitis E is spread in a similar fashion to hepatitis A and is found primarily in Asia, the Middle East, Africa, and Central and South America, although increasing numbers of cases are being recognized in persons in the United States who have not traveled to these areas. Hepatitis E can rarely cause chronic hepatitis in persons whose immune system is not working properly.
Signs and symptoms of viral hepatitis correspond to those of hepatitis in general. See the section on Signs and Symptoms for detailed information.
A variety of blood tests are available to help diagnose and/or monitor hepatitis caused by specific hepatitis viruses. For testing information on the most common causes of viral hepatitis, see the pages on hepatitis A, B, and C, or see the summary information in the table below.
Summary Table: Most common causes of viral hepatitis
|Virus||Hepatitis A||Hepatitis B||Hepatitis C|
|Transmission route||Fecal-oral||Infected blood, semen, or other body fluids||Infected blood, semen, or other body fluids|
|Incubation time (acute infection)||15-50 days||60-150 days||14-180 days|
|Onset||Sudden||Either sudden or slow, unnoticed||Usually slow, unnoticed|
|Severity||Mild||Occasionally severe||Usually slow-developing and symptoms not specific or strong|
|Associated with other diseases?||None||Liver cancer, cirrhosis||Liver cancer, cirrhosis|
|Testing to Diagnose Acute Infection||HAV-Ab, IgM||HBsAg, Anti-HBc, IgM||Anti-HCV, HCV RNA (Note: may have same results as in chronic hepatitis)|
|Testing to Diagnose Chronic Infection or to Monitor Treatment||N/A||HBsAg, HBV DNA, HBeAg, Anti-HBe||Anti-HCV (once), HCV RNA or viral load, HCV genotype (once)|
|Tests that Detect Previous Infection||HAV-Ab, IgG||Anti-HBs, Anti-HBc total||Anti-HCV|
|Common Treatment||None||Chronic form: Interferon, entecavir, tenofovir, lamivudine, adefovir||Treatment for acute HCV is similar to the chronic form. However, the best regimen and when to start treatment remains uncertain. Chronic HCV is usually treated with a combination of drugs. Some examples include a pill containing sofosbuvir and ledipasvir, and a multiple drug regimen containing ombitasvir, dasabuvir, paritaprevir, and ritonavir; a number of other combinations have been approved by the FDA recently, and more are likely to come in the future. Treatments may differ depending on a variety of factors, including HCV genotype and the health of the person's liver.|
The incidence of new cases of viral hepatitis has decreased due to use of safer injection and sex practices (important in preventing hepatitis B and C) and the availability of vaccines for hepatitis A and hepatitis B (there is currently no vaccine available for hepatitis C). Screening units of blood for hepatitis B and C has virtually eliminated infections through blood transfusions. A systematic program to screen pregnant mothers for hepatitis B and to vaccinate all newborns has greatly decreased new cases of hepatitis B.
Support and symptom relief are frequently the only treatments required for acute hepatitis A. This usually involves plenty of rest, fluids, and nutritious food. With hepatitis A, most people recover without complications.
Management of acute hepatitis B is primarily supportive and usually involves plenty or rest and fluids and good nutrition. For those who progress to the chronic form of hepatitis B, management goals include minimizing further damage to the liver, treating underlying conditions that are causing or exacerbating the condition, and preventing transmission of the virus. There are medications available to treat chronic hepatitis B, but not all people need to be treated. People with chronic hepatitis are closely monitored for the development of liver cirrhosis or cancer.
About 75-85% of people with acute hepatitis C develop the chronic form and both forms can be treated, usually with a combination of drugs. Though acute HCV can be cleared by some people without medications, treatment reduces the risk that the infection will become chronic. The same drugs used to treat chronic hepatitis C are used to treat the acute form, but the best treatment for acute HCV and when to start it remains uncertain.
The approach to treating chronic hepatitis C varies based on the genetic makeup (genotype) of HCV that is causing the infection, whether a person has previously been treated for HCV infection, the health of the person's liver, and other factors. A current list of approved drugs used to treat hepatitis C can be found by visiting the U.S. Food and Drug Administration web site.