- Viral hepatitis
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MeshID = D006525
Viral hepatitis is the cause of most cases of acute
hepatitis. Types include Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis B with D, Hepatitis E, Hepatitis F virus(existence unknown), and Hepatitis Gor GBV-C.
In addition to the
hepatitis viruses, other viruses can also cause hepatitis, including cytomegalovirus, Epstein-Barr virus, yellow fever, etc.
Hepatitis Aor infectious jaundiceis caused by a picornavirustransmitted by the fecal-oral route, often associated with ingestionof contaminated foodor with anal/oral sex. It causes an acute form of hepatitis and does not have a chronic stage. The patient's immune systemmakes antibodiesagainst hepatitis A that confer immunityagainst future infection. People with hepatitis Aare advised to rest, stay hydratedand avoid alcohol. A vaccineis available that will prevent infectionfrom hepatitis A for up to 10 years. Hepatitis A can be spread through personal contact, consumption of raw sea foodor drinking contaminated water. This occurs primarily in third world countries. Strict personal hygieneand the avoidance of raw and unpeeled foodscan help prevent an infection. Infected people excrete the hepatitis A virus with their fecestwo weeks before and one week after the appearance of jaundice. The time between the infectionand the start of the illnessaverages 28 days (ranging from 15 to 50 days), [cite web | title = CDC Hepatitis A FAQ | url=http://www.cdc.gov/ncidod/diseases/hepatitis/a/faqa.htm#general | accessdate = 2008-03-03] and most recover fully within 2 months, although approximately 15% of sufferersmay experience continuous or relapsing symptomsfrom six months to a year following initial diagnosis. [cite web | title = CDC Hepatitis A Fact Sheet | url=http://www.cdc.gov/ncidod/diseases/hepatitis/a/fact.htm | accessdate = 2008-03-03]
Hepatitis Bis caused by a hepadnavirus, which can cause both acute and chronic hepatitis. Chronic hepatitis develops in the 15% of patients who are unable to eliminate the virus after an initial infection. Identified methods of transmission include blood( blood transfusion, now rare), tattoos (both amateur and professionally done), sexually (through sexual intercourseor through contact with bloodor bodily fluids), or via mother to child by breast feeding(minimal evidence of transplacental crossing). However, in about half of cases the source of infection cannot be determined. Blood contactcan occur by sharing syringes in intravenous druguse, shaving accessoriessuch as razor blades, or touching woundson infected persons. Needle-exchange programmes have been created in many countries as a form of prevention.
Patients with chronic
hepatitis Bhave antibodiesagainst hepatitis B, but these antibodiesare not enough to clear the infectionthat establishes itself in the DNAof the affected liver cells. The continued production of viruscombined with antibodiesis a likely cause of the immune complex diseaseseen in these patients. A vaccineis available that will prevent infectionfrom hepatitis Bfor life. Hepatitis B infectionsresult in 500,000 to 1,200,000 deathsper year worldwidedue to the complicationsof chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Hepatitis Bis endemic in a number of (mainly South-East Asian) countries, making cirrhosisand hepatocellular carcinoma big killers. There are six FDA-approved treatment options available for persons with a chronic hepatitis B infection: alpha-interferon, pegylated interferon adefovir, entecavir, telbivudineand lamivudine. About 65% of persons on treatmentachieve a sustained response.
Hepatitis C(originally "non-A non-B hepatitis") is caused by a viruswith an RNA genomethat is a member of the Flaviviridaefamily. It can be transmitted through contact with blood(including through sexual contactif the two parties' bloodis mixed) and can also cross the placenta. Hepatitis C may lead to a chronic form of hepatitis, culminating in cirrhosis. It can remain asymptomaticfor 10-20 years. Patients with hepatitis C are susceptible to severe hepatitis if they contract either hepatitis A or B, so all hepatitis C patients should be immunizedagainst hepatitis A and hepatitis B if they are not already immune, and avoid alcohol. The viruscan cause cirrhosisof the liver. HCV virallevels can be reduced to undetectable levels by a combination of interferonand the antiviral drug ribavirin. The genotypeof the virusdetermines the rate of response to this treatment regimen. Genotype 1is more resistant to interferon therapythan other HCV genotypes.
Hepatitis C is the most common bloodborne infection in the United States.
Hepatitis Dis caused by hepatitis delta agent, which is similar to a viroidas it can only propogate in the presence of the Hepatitis Bvirus.
Hepatitis Eproduces symptoms similar to hepatitis A, although it can take a fulminant course in some patients, particularly pregnant women; it is more prevalent in the Indian subcontinent.
Hepatitis F virus
Hepatitis F virusis a hypothetical viruslinked to hepatitis. Several hepatitis F viruscandidates emerged in the 1990s; none of these reports have been substantiated.
Hepatitis G, now called
GB virus C
Another potential viral cause of hepatitis, initially identified as
hepatitis Gvirus, [cite journal |author=Linnen J, Wages J, Zhang-Keck ZY, "et al" |title=Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent |journal=Science (journal) |volume=271 |issue=5248 |pages=505–8 |year=1996 |pmid=8560265 |doi=10.1126/science.271.5248.505 |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=8560265] is probably spread by blood and sexual contact. [cite journal
author = Stark J, "et al"
title = Detection of the hepatitis G virus genome among injecting drug users, homosexual and bisexual men, and blood donors
journal =J. Infect. Dis.
volume = 174
issue = 6
pages = 1320–3
pmid = 8940225 ] There is very little evidence that this virus causes hepatitis, as it does not appear to replicate primarily in the liver. [cite journal |author=Pessoa MG, Terrault NA, Detmer J, "et al" |title=Quantitation of hepatitis G and C viruses in the liver: evidence that hepatitis G virus is not hepatotropic |journal=Hepatology |volume=27 |issue=3 |pages=877–80 |year=1998 |pmid=9500722 |doi=10.1002/hep.510270335 |url=] It is now classified as
GB virus C. [cite web |url=http://phene.cpmc.columbia.edu/Ictv/fs_flavi.htm#Genus0 |title=00.026. Flaviviridae - ICTVdB Index of Viruses |format= |work= |accessdate=]
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