In general, hepatitis is any inflammation of the liver. General symptoms include jaundice, fever, appetite loss and gastrointestinal upset. Jaundice, also called icterus, is a yellowing of the skin caused by the buildup of bile pigments (bilirubins) in the bloodstream. Hepatitis is mostly caused by liver infections, typically viral ones, but it can also be caused by exposure to toxic drugs and other chemicals that irritate and poison the liver.
Hepatitis can be an acute disease that makes the patient very sick and then they recover, but it can also result in a chronic disease that's hard to get rid of and can ultimately result in liver cancer or liver failure.
A rare, severe complication of viral hepatitis is a condition called icterus gravis, or massive hepatic necrosis. A person suffering from this condition experiences jaundice, high fever, and delirium. Their bile ducts will be almost entirely blocked, and parts of their liver will die. While the liver may regenerate after the disease has passed, it may also end up with severe scarring (cirrhosis). In the worst cases, the person may lose liver function entirely and need a liver transplant to survive.
There are several types of viral hepatitis; hepatitis A and B are the most common types and are caused by members of the family Hepadnaviridae, but other versions (C through F) are caused by water-borne calciviruses and togoviruses.
Of all the acute hepatitis cases in the United States from 1982-1993, 47% were caused by hepatitis A, 34% by hepatitis B, 16% by hepatitis C, and 3% by some other infection. However, of the potentially-fatal chronic cases, hepatitis B and C cause the most cases with hepatitis C being overall the biggest killer.
This type of hepatitis is also known in some literature as "infectious hepatitis" or "epidemic jaundice". It is caused by RNA viruses in the genus Enterovirus. The disease it causes is usually fairly mild; people may mistake it for the flu. The virus typically spreads through food or water contaminated with infected feces and is most prevalent in places where people don't practice good hygiene. It can also be contracted through sex and other bodily fluid contact.
Most people start getting sick about 28 days after they've been infected. However, the incubation can range from 15–50 days.
In the U.S., about 33% of all adults have antibodies for hepatitis A, indicating that they've been infected with it at some point. It can spread rapidly and occur at epidemic rates in communities and countries.
This form of hepatitis usually clears up on its own within two months, but in serious cases it is treated with injections of gamma globulins to boost the patient's immune system. About 15% of all infectees will have chronic or relapsing symptoms within a 6-9 month period and require treatment. A vaccine is available to prevent the illness in places where good personal hygiene and proper sanitation can't be maintained.
This disease is also known as "serum hepatitis" and "homologous serum jaundice". It is caused by DNA viruses in the family Hepadnaviridae and is much more serious than hepatitis A. Hepatitis B has a long incubation period (around three months) and can cause severe liver damage and even death. It is typically spread by blood or body fluid contact, such as through hypodermic needles or sexual intercourse.
People typically start getting sick about 60-90 days after infection; however, the incubation can range from 45 to 180 days.
Up to 25% of all those who suffer from chronic hepatitis B infections will die from the damage caused to their liver. The younger the person gets this disease, the worse their chances: 6% of all infected people older than 5 years will develop chronic disease, but 90% of all infants infected at birth will. A type of liver cancer, hepatoma, can also follow a bout with hepatitis B. Nearly 80,000 people in the U.S. are infected, and about 5,000 die every year.
People can protect themselves by getting a vaccination against the Hepatitis B virus and by using condoms and taking other precautions against being exposed to body fluids from infected people. Such infections can be treated with the antiviral drugs alpha interferon, adefovir dipivoxil, and lamivudine.
Hepatitis C is a serious disease caused by either of two types of unclassified hepatitis-causing viruses. One version, caused by a calicivirus, spreads via water. The other, from a togovirus, tends to occur after blood transfusions or other blood contact.
People typically start getting sick about 6-7 weeks after infection, but they may show symptoms as early as two weeks or as late as six months.
Hepatitis C is the culprit behind 60-70% of the chronic hepatitis cases in the U.S. More importantly, it's responsible for as much as half of all the cases of fatal liver disease and liver cancer in the U.S.; it kills 8,000-10,000 people in the U.S. every year (statistics in other industrialized countries seem comparable).
There is no vaccine against this disease, so the only way to prevent it is to avoid blood contact with infected people. This disease can be successfully treated with a combination of two antiviral drugs: alpha interferon and ribavirin.
Hepatitis D (Delta)
Hepatitis delta is a severe form of hepatitis which arose recently. It is caused by a combination of the delta virus and the virus which causes hepatitis B.
The hepatitis delta virus is a defective virus which uses single-stranded RNA as its genetic material. It is only able to replicate when a helper virus from the family Hepadnaviridae is present in the same host cell.
Up to 80% of all infectees develop cirrhosis and chronic liver disease from this infection. It can be treated with alpha interferon.
This is also known as "non-A, non-B hepatitis" in some older literature. It is a spherical, non-enveloped, single stranded RNA virus of about 32 to 34 nanometers in diameter. It causes disease very similar to hepatitis A, and has an incubation period of 15-60 days with 40 days being typical. No infectees have been found to develop chronic disease. Hepatitis E is rare in the U.S. but is common in Africa and Southeast Asia.
References: multiple CDC factsheets and my biology textbook