Hepatitis A
344536
220143453
2008-06-18T14:04:06Z
Gail
7214503
Reverted edits by [[Special:Contributions/87.84.27.62|87.84.27.62]] to last version by GrahamColm (using [[WP:HG|Huggle]])
{{Taxobox
| name = Hepatitis A
| image = Hepatitis A virus 02.jpg
| image_caption = [[electron microscope|Electron micrograph]] of hepatitis A virions.
| image_width = 185px
| virus_group = iv
| familia = ''[[Picornaviridae]]''
| genus = ''Hepatovirus''
| type_species = ''[[Hepatitis A virus]]''
}}
{{DiseaseDisorder infobox |
Name = Hepatitis A |
ICD10 = {{ICD10|B|15||b|15}}- |
ICD9 = {{ICD9|070.1}} |
DiseasesDB = 5757|
MedlinePlus = 000278|
eMedicineSubj = med|
eMedicineTopic = 991|
eMedicine_mult = {{eMedicine2|ped|977}} |
MeshID = D006506 |
}}
'''Hepatitis A''', (formerly known as ''infectious hepatitis''), is an [[Acute (medical)|acute]] [[infectious disease]] of the [[liver]] caused by Hepatitis A virus,<ref name=Sherris>{{cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | pages = 541–4 | publisher = McGraw Hill | year = 2004 | isbn = 0838585299 }}</ref> which is most commonly transmitted by the [[fecal-oral route]] via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus.<ref name="pmid9556642">{{cite journal
|author=Thiel TK
|title=Hepatitis A vaccination
|journal=Am Fam Physician
|volume=57
|issue=7
|pages=1500
|year=1998
|pmid=9556642
}}</ref> The time between infection and the appearance of the symptoms, (the [[incubation period]]), is between two and six weeks and the average incubation period is 28 days.<ref name="pmid16271543">{{cite journal
|author=Connor BA
|title=Hepatitis A vaccine in the last-minute traveler
|journal=Am. J. Med.
|volume=118 Suppl 10A
|issue=
|pages=58S–62S
|year=2005
|pmid=16271543
|doi=10.1016/j.amjmed.2005.07.018
|url=http://linkinghub.elsevier.com/retrieve/pii/S0002-9343(05)00611-X
}}</ref>
In [[developing country|developing countries]], and in regions with poor hygiene standards, the [[incidence (epidemiology)|incidence]] of infection with this virus approaches 100% and the illness is usually contracted in early childhood. Hepatitis A infection causes no clinical signs and symptoms in over 90% of these children and since the infection confers lifelong immunity, the disease is of no special significance to the [[indigenous]] population. In Europe, the United States and other industrialised countries, on the other hand, the infection is contracted primarily by [[susceptible]] young adults, most of whom are infected with the virus during trips to countries with a high incidence of the disease.<ref name="pmid16271543">{{cite journal
|author=Connor BA
|title=Hepatitis A vaccine in the last-minute traveler
|journal=Am. J. Med.
|volume=118 Suppl 10A
|issue=
|pages=58S–62S
|year=2005
|pmid=16271543
|doi=10.1016/j.amjmed.2005.07.018
|url=http://linkinghub.elsevier.com/retrieve/pii/S0002-9343(05)00611-X
}}</ref>
Hepatitis A does not have a [[Chronic (medicine)|chronic]] stage and does not cause permanent liver damage. Following infection, the [[immune system]] makes [[Antibody|antibodies]] against the hepatitis A virus that confer immunity against future infection. The disease can be prevented by [[vaccination]] and [[hepatitis A vaccine]] has been proved effective in controlling outbreaks worldwide.<ref name="pmid16271543">{{cite journal
|author=Connor BA
|title=Hepatitis A vaccine in the last-minute traveler
|journal=Am. J. Med.
|volume=118 Suppl 10A
|issue=
|pages=58S–62S
|year=2005
|pmid=16271543
|doi=10.1016/j.amjmed.2005.07.018
|url=http://linkinghub.elsevier.com/retrieve/pii/S0002-9343(05)00611-X
}}</ref>
==Virus==
The Hepatitis [[virus]] (HAV) is a [[Picornavirus]]; it is [[Viral envelope|non-enveloped]] and contains a [[Positive-sense ssRNA virus|single-stranded RNA ]] packaged in a protein [[capsid|shell]]. There is only one [[serovar|type]] of the virus.
== Pathogenesis ==
Following ingestion, HAV enters the bloodstream through the epithelium of the [[oropharynx]] or intestine.<ref>Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). ''Medical Microbiology," 5th ed., Elsevier Mosby.</ref> The blood carries the virus to its target, the liver, where it lives and multiplies within [[hepatocytes]] and [[Kupffer cells]] (i.e., liver macrophages). There is no apparent virus-mediated [[cytotoxicity]], and liver pathology is likely immune-mediated. [[Virions]] are secreted into the [[bile]] and released in stool. HAV is excreted in large quantities approximately 11 days prior to appearance of symptoms or anti-HAV [[IgM]] [[antibodies]] in the blood. The [[incubation period]] is 15-50 days, and mortality is less than 0.5%.
==Transmission==
The virus spreads by the [[fecal-oral route]] and infections often occur in conditions of poor sanitation and overcrowding. Hepatitis A can be transmitted by the [[parenteral]] route but very rarely by blood and blood products. Food-borne outbreaks are not uncommon,<ref name="pmid16848078">{{cite journal
|author=Brundage SC, Fitzpatrick AN
|title=Hepatitis A
|journal=Am Fam Physician
|volume=73
|issue=12
|pages=2162–8
|year=2006
|pmid=16848078
}}</ref> and ingestion of [[shellfish]] cultivated in polluted water is associated with a high risk of infection.<ref name="pmid10946842">{{cite journal
|author=Lees D
|title=Viruses and bivalve shellfish
|journal=Int. J. Food Microbiol.
|volume=59
|issue=1-2
|pages=81–116
|year=2000
|pmid=10946842
|url=http://linkinghub.elsevier.com/retrieve/pii/S0168-1605(00)00248-8
|doi=10.1016/S0168-1605(00)00248-8}}</ref>
Approximately 40% of all acute viral hepatitis is caused by HAV.<ref>Insert footnote text Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). ''Medical Microbiology," 5th ed., Elsevier Mosby.</ref> Infected individuals are infectious prior to onset of symptoms, roughly 10 days following infection. The virus is resistant to [[detergent]], acid (pH 1), solvents (e.g., [[ether]], [[chloroform]]), drying, and temperatures up to 60<sup>o</sup>C. It can survive for months in fresh and salt water. Common-source (e.g., water, restaurant) outbreaks are typical. Infection is common in children in developing countries, reaching 100% [[incidence]], but following infection there is life-long [[immunity]]. HAV can be inactivated by: [[chlorine]] treatment (drinking water), [[formalin]] (0.35%, 37<sup>o</sup>C, 72 hours), [[peracetic acid]] (2%, 4 hours), beta-propiolactone (0.25%, 1 hour), and [[UV radiation]] (2 μW/cm<sup>2</sup>/min).
==Symptoms==
Early symptoms of hepatitis A infection can be mistaken for [[influenza]], but some sufferers, especially children, exhibit no symptoms at all. Symptoms typically appear 2 to 6 weeks, (the [[incubation period]] ), after the initial infection.<ref>{{cite web | title = Hepatitis A Symptoms | publisher = eMedicineHealth | url = http://www.emedicinehealth.com/hepatitis_a/page3_em.htm#Hepatitis%20A%20Symptoms | date = 2007-05-17 | accessdate = 2007-05-18}}</ref>
Symptoms can return over the following 6-9 months which include:<ref>{{cite web | title = Hepatitis A : Fact Sheet | publisher = Center for Disease Control | url = http://www.cdc.gov/Ncidod/diseases/hepatitis/a/fact.htm | date = 2007-08-09 | accessdate = 2007-12-07}}</ref>
<div class="references-small" style="-moz-column-count:2; column-count:2;">
*[[Fatigue (medical)|Fatigue]]
*[[Fever]]
*[[Abdominal pain]]
*[[Nausea]]
*[[Diarrhea]]
*[[Appetite loss]]
*[[Depression (mood)|Depression]]
*[[Jaundice]], a yellowing of the skin or whites of the eyes
*Sharp pains in the [[Right upper quadrant (abdomen)|right-upper quadrant]] of the abdomen
*[[Weight loss]]
</div>
==Diagnosis==
[[Image:HAV Infection.png|right|thumb|300px|Serum IgG, IgM and ALT following Hepatitis A virus infection]]
Although the virus is excreted in the feces towards the end of the [[incubation period]], specific diagnosis is made by the detection of Hepatitis A virus specific [[IgM]] [[antibody|antibodies]] in the blood.<ref name="pmid7876654">{{cite journal
|author=Stapleton JT
|title=Host immune response to hepatitis A virus
|journal=J. Infect. Dis.
|volume=171 Suppl 1
|issue=
|pages=S9–14
|year=1995
|pmid=7876654
}}</ref> IgM antibody is only present in the blood following an [[acute]] hepatitis A infection. It is detectable from one to two weeks after the initial infection and persists for up to 14 weeks. The presence of IgG antibody in the blood means that the acute stage of the illness is past and the person is immune to further infection. IgG antibody to HAV is also found in the blood following [[vaccination]] and tests for immunity to the virus are based on the detection of this antibody.<ref name="pmid7876654">{{cite journal
|author=Stapleton JT
|title=Host immune response to hepatitis A virus
|journal=J. Infect. Dis.
|volume=171 Suppl 1
|issue=
|pages=S9–14
|year=1995
|pmid=7876654
}}</ref>
During the acute stage of the infection, the liver enzyme [[alanine transferase]] (ALT) is present in the blood at levels much higher than is normal. The [[enzyme]] comes from the liver cells that have been damaged by the virus.<ref name="pmid15931347">{{cite journal
|author=Musana KA, Yale SH, Abdulkarim AS
|title=Tests of liver injury
|journal=Clin Med Res
|volume=2
|issue=2
|pages=129–31
|year=2004
|pmid=15931347
|url=http://www.clinmedres.org/cgi/pmidlookup?view=long&pmid=15931347
}}</ref>
Hepatitis A virus is present in the blood, ([[viremia]]), and feces of infected people up to two weeks before clinical illness develops.<ref name="pmid15931347">
==Treatment==
There is no specific treatment for hepatitis A. Sufferers are advised to rest, avoid fatty foods and alcohol (these may be poorly tolerated for some additional months during the recovery phase and cause minor relapses), eat a well-balanced diet, and stay hydrated. Approximately 15% of people diagnosed with hepatitis A may experience one or more symptomatic relapse(s) for up to 24 months after contracting this disease.{{Fact|date=February 2008}}
==Prognosis==
The [[United States]] [[Centers for Disease Control and Prevention]] (CDC) in 1991 reported a low [[mortality rate]] for hepatitis A of 4 deaths per 1000 cases for the general [[population]] but a higher rate of 17.5 per 1000, in those aged 50 and over. Death usually occurs when the patient contracts Hepatitis A while already suffering from another form of Hepatitis, such as [[Hepatitis B]] or [[Hepatitis C]] or [[AIDS]].{{Fact|date=February 2008}}
Young children who are infected with hepatitis A typically have a milder form of the disease, usually lasting from 1-3 weeks, whereas adults tend to experience a much more severe form of the disease.{{Fact|date=February 2008}}
==Prevention==
Hepatitis A can be prevented by [[Hepatitis A vaccine|vaccination]], good [[hygiene]] and [[sanitation]].{{Fact|date=February 2008}}
==Vaccine==
{{Mainarticle|Hepatitis A vaccine}}
Hepatitis A vaccines protect against the virus. Vaccines contain inactivated Hepatitis A virus providing active immunity against a future infection.<ref name=Avaxim>{{cite web | title = Avaxim | work = NetDoctor.co.uk | url = http://www.netdoctor.co.uk/medicines/100003051.html | accessdate = 2007-03-12}}</ref>
==Epidemiology==
[[Image:HAV prevalence 2005.png|thumb|right|200px|Hepatitis A Distribution 2005]]
HAV is found in the feces of infected persons and those who are at higher risk include travelers to [[developing countries]] where there is a higher [[incidence (epidemiology)|incidence]] rate,<ref>[http://wwwn.cdc.gov/travel/yellowBookCh4-HepA.aspx#362 Chapter 4 - Hepatitis, Viral, Type A - Yellow Book | CDC Travelers' Health<!-- Bot generated title -->]</ref> and those having sexual contact or drug use with infected persons.<ref>[http://www.cdc.gov/Ncidod/diseases/hepatitis/a/fact.htm Hepatitis A: Fact Sheet | CDC Viral Hepatitis<!-- Bot generated title -->]</ref>
There were 30,000 cases of Hepatitis A reported to the CDC in the U.S. in 1997. The agency estimates that there were as many as 270,000 cases each year from 1980 through 1999.<ref>http://www.cdc.gov/Ncidod/diseases/hepatitis/a/global_hepA_epi.pdf</ref>
HAV outbreaks still occur in and caused by poor hand hygiene among infected, sometimes symptomatic restaurant employees failing to wash their hands after [[toilet]] breaks.
===Epidemics===
The most widespread hepatitis A outbreak in America afflicted at least 640 people (killing four) in north-eastern [[Ohio]] and south-western [[Pennsylvania]] in late 2003. The outbreak was blamed on tainted [[green onion]]s at a restaurant in [[Monaca, Pennsylvania]].<ref>http://www.cdc.gov/mmwR/preview/mmwrhtml/mm5247a5.htm</ref> In 1988, 300,000 people in Shanghai, China were infected with HAV after eating clams from a contaminated river.<ref> Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). ''Medical Microbiology," 5th ed., Elsevier Mosby. </ref>
==See also==
*[[Hepatitis]]
*[[Hepatitis B]]
*[[Hepatitis C]]
*[[Hepatitis E]]
*[[Maurice Hilleman]]
==References==
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==External links==
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*[http://www3.niaid.nih.gov/ NIAID] Bioinformatics Resource Center)
*[http://www.cdc.gov/ncidod/diseases/hepatitis/a/index.htm CDC's hepatitis A links]
*[http://www.cdc.gov/ncidod/diseases/hepatitis/a/fact.htm CDC's hepatitis A Fact Sheet]
* {{MeshName|Hepatitis+A}}
* {{MeshName|Hepatitis+A+virus}}
{{Viral diseases}}
[[Category:Foodborne illnesses]]
[[Category:hepatitis|A]]
[[Category:Picornaviruses]]
[[Category:Viral diseases]]
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