- Hepatitis A
| MeshID = D006506
Hepatitis A, (formerly known as "infectious hepatitis"), is an acute
infectious disease of theliver caused by Hepatitis A virus,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 ] which is most commonly transmitted by thefecal-oral route via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus.cite journal
author=Thiel TK
title=Hepatitis A vaccination
journal=Am Fam Physician
volume=57
issue=7
pages=1500
year=1998
pmid=9556642] The time between infection and the appearance of the symptoms, (theincubation period ), is between two and six weeks and the average incubation period is 28 days.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]In developing countries, and in regions with poor hygiene standards, the 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 industrialized countries, on the other hand, the infection is contracted primarily bysusceptible young adults, most of whom are infected with the virus during trips to countries with a high incidence of the disease.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]Hepatitis A does not have a chronic stage and does not cause permanent liver damage. Following infection, the
immune system makes antibodies against the hepatitis A virus that confer immunity against future infection. The disease can be prevented byvaccination andhepatitis A vaccine has been proved effective in controlling outbreaks worldwide.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]Virus
The Hepatitis
virus (HAV) is aPicornavirus ; it is non-enveloped and contains a single-stranded RNA packaged in a protein shell. There is only one type of the virus.Pathogenesis
Following ingestion, HAV enters the bloodstream through the epithelium of the
oropharynx or intestine. [Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). "Medical Microbiology," 5th ed., Elsevier Mosby.] The blood carries the virus to its target, the liver, where it lives and multiplies withinhepatocytes andKupffer cells (i.e., liver macrophages). There is no apparent virus-mediatedcytotoxicity , and liver pathology is likely immune-mediated.Virions are secreted into thebile and released in stool. HAV is excreted in large quantities approimately 11 days prior to appearance of symptoms or anti-HAVIgM antibodies in the blood. Theincubation 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 theparenteral route but very rarely by blood and blood products. Food-borne outbreaks are not uncommon,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] and ingestion ofshellfish cultivated in polluted water is associated with a high risk of infection.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)00248-8doi=10.1016/S0168-1605(00)00248-8] Approximately 40% of all acute viral hepatitis is caused by HAV. [Insert footnote text Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). "Medical Microbiology," 5th ed., Elsevier Mosby.] 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 60oC. 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-longimmunity . HAV can be inactivated by:chlorine treatment (drinking water),formalin (0.35%, 37oC, 72 hours),peracetic acid (2%, 4 hours), beta-propiolactone (0.25%, 1 hour), andUV radiation (2 μW/cm2/min).ymptoms
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, (theincubation period ), after the initial infection. [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]Symptoms can return over the following 6-9 months which include: [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]
*Fatigue
*Fever
*Abdominal pain
*Nausea
*Diarrhea
*Appetite loss
*Depression
*Jaundice , a yellowing of the skin or whites of the eyes
*Sharp pains in the right-upper quadrant of the abdomen
*Weight loss
*Itching Diagnosis
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 specificIgM antibodies in the blood.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] IgM antibody is only present in the blood following anacute 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 followingvaccination and tests for immunity to the virus are based on the detection of this antibody.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]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. Theenzyme comes from the liver cells that have been damaged by the virus.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]Hepatitis A virus is present in the blood, (
viremia ), and feces of infected people up to two weeks before clinical illness develops.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 lowmortality rate for hepatitis A of 4 deaths per 1000 cases for the generalpopulation 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 asHepatitis B orHepatitis C orAIDS .Fact|date=February 2008Young 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 vaccination, good
hygiene andsanitation .Fact|date=February 2008Vaccine
Hepatitis A vaccines protect against the virus. Vaccines contain inactivated Hepatitis A virus providing active immunity against a future infection.cite web | title = Avaxim | work = NetDoctor.co.uk | url = http://www.netdoctor.co.uk/medicines/100003051.html | accessdate = 2007-03-12]
Epidemiology
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 rate, [ [http://wwwn.cdc.gov/travel/yellowBookCh4-HepA.aspx#362 Chapter 4 - Hepatitis, Viral, Type A - Yellow Book | CDC Travelers' Health ] ] and those having sexual contact or drug use with infected persons. [ [http://www.cdc.gov/Ncidod/diseases/hepatitis/a/fact.htm Hepatitis A: Fact Sheet | CDC Viral Hepatitis ] ] 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 2000. [ [http://www.cdc.gov/Ncidod/diseases/hepatitis/a/global_hepA_epi.pdf Index | CDC Viral Hepatitis ] ]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 the United States afflicted at least 640 people (killing four) in north-eastern
Ohio and south-westernPennsylvania in late 2003. The outbreak was blamed on taintedgreen onion s at a restaurant inMonaca, Pennsylvania . [ [http://www.cdc.gov/mmwR/preview/mmwrhtml/mm5247a5.htm Hepatitis A Outbreak Associated with Green Onions at a Restaurant - Monaca, Pennsylvania, 2003 ] ] In 1988, 300,000 people in Shanghai, China were infected with HAV after eating clams from a contaminated river. [ Murray, P. r., Rosenthal, K. S., & Pfaller, M. A. (2005). "Medical Microbiology," 5th ed., Elsevier Mosby. ]ee also
*
Hepatitis
*Hepatitis B
*Hepatitis B in China
*Hepatitis C
*Hepatitis D
*Hepatitis E
*Hepatitis F
*Hepatitis G
*Maurice Hilleman References
External links
* [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]
*
*
Wikimedia Foundation. 2010.
