Hepatitis is any of a group of diseases characterized by inflammation of the liver triggered by wide-ranging causative agents. There are several causes of liver inflammation leading to hepatitis, including infection as well as environmental and immunologic causes.
There are three noninfectious hepatitis diseases: alcoholic hepatitis, autoimmune hepatitis, and nonalcoholic steatohepatitis (NASH). Alcoholic hepatitis is caused by chronic alcohol consumption, autoimmune hepatitis is caused when the body’s immune system attacks the liver, and nonalcoholic steatohepatitis happens when excessive fat storage in the liver results in fatty liver disease. Both general fatty liver disease and its more dangerous form, NASH, are noninfectious types of hepatitis.
Infectious hepatitis can be caused by any one of the five unrelated hepatitis viruses, A, B, C, D, or E. These are the viruses that cause liver diseases of the same names, and most cases of hepatitis are caused by viral infection. Symptoms of hepatitis include jaundice, or yellowing of the skin and eyes, loss of appetite, stomach pain, nausea, and vomiting.
Hepatitis caused by viral infection can be a chronic or acute disease. The hepatitis A and E viruses typically cause an acute infection, hepatitis B and C can cause chronic or acute infections, and hepatitis D causes chronic infection in patients already infected with hepatitis B. Acute hepatitis typically clears on its own within a few weeks, without the need for medical intervention. Conversely, chronic hepatitis can cause long-term symptoms that must be treated by medical professionals. Hepatitis can cause scarring of the liver, known as cirrhosis, and sometimes causes severe damage that requires a liver transplant. Chronic hepatitis may also lead to the development of liver cancer.
Hepatitis B and C can be transmitted by contact with infected bodily fluids, including blood, while hepatitis A and E are commonly transmitted by contaminated food or water and/or ingestion of contaminated feces. These methods of transmission occur most frequently in countries with poor sanitation. Due to its presence in blood, semen, and other body fluids of infected persons, hepatitis B virus is transmitted by shared drug-injection devices (needles, syringes, etc.), through sexual contact, or from an infected mother to her baby during birth. Likewise, the presence of hepatitis C virus in the blood of infected persons enables it to be transmitted via shared needles and syringes and via sexual contact. After infection the hepatitis virus can remain dormant in the infected individual for one to three months before symptoms of the disease emerge.
There are now vaccines for hepatitis A and B, which can prevent infection with these two strains of virus. There is no vaccine for the other most common strain of hepatitis, hepatitis C, or for hepatitis D or E. Other viruses, including cytomegalovirus, Epstein-Barr, and the yellow fever virus, may also trigger hepatitis, though commonly less severe forms.
Viral Infections Diagnosed by Immunoassay of Stool
| Causative Agent | Description | Transmission | Symptoms | Treatment |
|---|---|---|---|---|
| Astroviruses | RNA(+) viruses, infants and children are most susceptible, causes damage to intestinal epithelium | Fecal-oral, contaminated food | Abdominal pain, diarrhea, fatigue, fever, headache, vomiting | Rehydration and supportive care |
| Hepatitis D virus | Deltavirus with circular ssRNA(-) genome, requires current infection with hepatitis B virus to replicate | Blood-blood contact | Enhances symptoms and severity of hepatitis B infection | Prevented with hepatitis B vaccine; interferon |
| Norovirus (Norwalk-like viruses) | RNA(+) viruses, highly contagious and spreads through confined spaces (cruise ships, military barracks) rapidly, most common in children and the elderly | Airborne, fecal-oral, fomites, contaminated food | Cramps, diarrhea with dehydration, fever, violent vomiting | Self-limiting, rehydration and supportive care; no vaccines or therapies are available; handwashing and good hygiene for prevention |
| Rotavirus | ds-RNA viruses, most common in children and those with weakened immune systems, replicates in epithelial cells of intestinal villi | Fecal-oral, fomites | Asymptomatic or subclinical in those previously infected; diarrhea with dehydration, fever, vomiting | Prevented with vaccination; rehydration and supportive care |
Diagnosis of stool samples is one way of determining the presence of digestive diseases caused by viruses. With the exception of hepatitis viruses, viral digestive diseases are commonly fast acting and self-limiting.
Viral Infections Diagnosed by Immunoassay of Blood
| Causative Agent | Description | Transmission | Symptoms | Treatment |
|---|---|---|---|---|
| Hepatitis A virus | Picornaviridae virus with ssRNA(+) genome | Fecal-oral, consumption of contaminated food or water | Acute: abdominal pain, appetite suppression, diarrhea, fever, jaundice, vomiting.
Chronic: cirrhosis, liver inflammation, liver cancer. |
Prevented with vaccination. No treatments are available. |
| Hepatitis B virus | Hepadnavirus with circular, partially dsDNA genome | Blood or body fluid contact | Acute: appetite suppression, body aches, discolored urine, fever, jaundice, vomiting.
Chronic: cirrhosis, liver inflammation, liver cancer. |
Prevented with vaccination. Typically left untreated; antiviral therapy and immune modulators (interferon) may slow replication in chronic infections, reducing liver cancer risk. |
| Hepatitis C virus | Flaviviridae virus with ssRNA(+) genome. Several subtypes exist. | Blood-blood contact | Acute: generally mild, appetite suppression, fatigue, fever, nausea, pain, weight loss.
Chronic: cirrhosis, liver cancer. |
Antiviral therapy that is dependent on the subtype of the virus |
| Hepatitis D virus | Deltavirus with circular ssRNA(-) genome, requires current infection with hepatitis B virus to replicate | Blood-blood contact | Enhances symptoms and severity of hepatitis B infection | Prevented with hepatitis B vaccine; interferon |
| Hepatitis E virus | Hepeviridae virus with ssRNA(+) genome, four different genotypes | Genotype dependent: fecal-oral, or zoonotic and acquired from ingesting meat from an infected animal | Fatigue, jaundice, nausea | Self-limiting. Antiviral and immune modulators may be administered to immunocompromised patients. |
Using blood immunoassays is one way to determine viral infections of the digestive system. These include the series of hepatitis viruses.