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| ==Overview== | | ==Overview== |
| | [[Hepatitis A virus]] was first identified in 1973. It was classified as a separate disease from other types of [[hepatitis]] during World War II. However, its true [[prevalence]] and route of [[transmission]] would only be recognized later. During 1995-1996, the Food and Drug Administration (FDA) approved the inactivated hepatitis A vaccine. Consequently, [[hepatitis A]] became a disease that was not only common but also vaccine-preventable. |
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| ==Historical Perspective== | | == Historical Perspective == |
| Hepatitis A virus was first identified in 1973.
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| ===Prevaccine Era===
| | The earliest descriptions of diseases similar to [[Hepatitis A virus]] were reported 5000 years ago in China. Hippocrates also described a disease resembling hepatitis A that he called benign epidemic jaundice <ref name="pmid29712682">{{cite journal| author=Feinstone SM| title=History of the Discovery of Hepatitis A Virus. | journal=Cold Spring Harb Perspect Med | year= 2019 | volume= 9 | issue= 5 | pages= | pmid=29712682 | doi=10.1101/cshperspect.a031740 | pmc=6496330 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=29712682 }} </ref>. |
| Hepatitis A epidemiology in the United States has fundamentally changed with licensure of hepatitis A vaccine and implementation of national ACIP recommendations for its use. Before vaccine licensure during 1995-1996, hepatitis A incidence was primarily cyclic, with peaks occurring every 10-15 years. In the United States, during 1980-1995, approximately 22,000-36,000 hepatitis A cases were reported annually to CDC (rate: 9.0-14.5 cases per 100,000 population), but incidence models indicate that the number of infections was substantially higher.<ref name="pmid11986444">{{cite journal |author=Armstrong GL, Bell BP |title=Hepatitis A virus infections in the United States: model-based estimates and implications for childhood immunization |journal=[[Pediatrics]] |volume=109 |issue=5 |pages=839–45 |year=2002 |month=May |pmid=11986444 |doi= |url=http://pediatrics.aappublications.org/cgi/pmidlookup?view=long&pmid=11986444 |accessdate=2012-02-28}}</ref><ref>CDC. Hepatitis surveillance. Report no. 61. Atlanta, GA: US Department of Health and Human Services, CDC. 2006</ref> One such analysis estimated an average of 271,000 infections per year during 1980-1999, representing 10.4 times the reported number of cases.<ref name="pmid11986444">{{cite journal |author=Armstrong GL, Bell BP |title=Hepatitis A virus infections in the United States: model-based estimates and implications for childhood immunization |journal=[[Pediatrics]] |volume=109 |issue=5 |pages=839–45 |year=2002 |month=May |pmid=11986444 |doi= |url=http://pediatrics.aappublications.org/cgi/pmidlookup?view=long&pmid=11986444 |accessdate=2012-02-28}}</ref> Each year in the United States, an estimated 100 persons died as a result of acute liver failure attributed to hepatitis A. | |
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| The costs associated with hepatitis A are substantial. Surveillance data indicate that 11%-22% of persons with hepatitis A are hospitalized.<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4812a1.htm CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1999;48(No. RR-12):1-37]</ref> The average duration of work loss for adults who become ill has been estimated at 15.5 days for nonhospitalized patients and 33.2 days for hospitalized patients.<ref name="pmid10655272">{{cite journal |author=Berge JJ, Drennan DP, Jacobs RJ, Jakins A, Meyerhoff AS, Stubblefield W, Weinberg M |title=The cost of hepatitis A infections in American adolescents and adults in 1997 |journal=[[Hepatology (Baltimore, Md.)]] |volume=31 |issue=2 |pages=469–73 |year=2000 |month=February |pmid=10655272 |doi=10.1002/hep.510310229 |url=http://dx.doi.org/10.1002/hep.510310229 |accessdate=2012-02-28}}</ref> Estimates of the annual direct and indirect costs of hepatitis A in the United States have ranged from $300 million to $488.8 million in 1997 dollars.<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4812a1.htm CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1999;48(No. RR-12):1-37]</ref><ref name="pmid10655272">{{cite journal |author=Berge JJ, Drennan DP, Jacobs RJ, Jakins A, Meyerhoff AS, Stubblefield W, Weinberg M |title=The cost of hepatitis A infections in American adolescents and adults in 1997 |journal=[[Hepatology (Baltimore, Md.)]] |volume=31 |issue=2 |pages=469–73 |year=2000 |month=February |pmid=10655272 |doi=10.1002/hep.510310229 |url=http://dx.doi.org/10.1002/hep.510310229 |accessdate=2012-02-28}}</ref> A recent Markov model analysis estimated economic costs of $133.5 million during the lifetime of a single age cohort of children born in 2005, in the absence of vaccination.
| | During the 17th century, outbreaks of hepatitis A were reported in military camps. In the US, first outbreak of more than 40,000 cases was reported in 1812 in Norfolk, VA. An estimated 16 million cases of hepatitis A were reported during the world war I and World War II <ref name="pmid29712682">{{cite journal| author=Feinstone SM| title=History of the Discovery of Hepatitis A Virus. | journal=Cold Spring Harb Perspect Med | year= 2019 | volume= 9 | issue= 5 | pages= | pmid=29712682 | doi=10.1101/cshperspect.a031740 | pmc=6496330 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=29712682 }} </ref>. |
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| ====Variation by Age, Race/Ethnicity, and Region====
| | Hepatitis A virus was first identified in 1973. In the US, hepatitis A vaccine was approved by the Food and Drug Administration (FDA) in 1995. |
| During the prevaccine era, the reported incidence of hepatitis A was highest among children aged 5-14 years, with approximately one third of reported cases involving children aged <15 years.<ref>CDC. Hepatitis surveillance. Report no. 61. Atlanta, GA: US Department of Health and Human Services, CDC. 2006</ref> Because young children frequently have unrecognized or asymptomatic infection, a relatively smaller proportion of infections among children than adults are detected by routine disease surveillance. Incidence models indicate that during 1980-1999, the majority of HAV infections occurred among children aged <10 years, and the highest incidence was among those aged 0-4 years.<ref name="pmid11986444">{{cite journal |author=Armstrong GL, Bell BP |title=Hepatitis A virus infections in the United States: model-based estimates and implications for childhood immunization |journal=[[Pediatrics]] |volume=109 |issue=5 |pages=839–45 |year=2002 |month=May |pmid=11986444 |doi= |url=http://pediatrics.aappublications.org/cgi/pmidlookup?view=long&pmid=11986444 |accessdate=2012-02-28}}</ref> Before the use of hepatitis A vaccine, rates among American Indians and Alaska Natives were more than five times higher than rates in other racial/ethnic populations, and rates among Hispanics were approximately three times higher than rates among non-Hispanics.<ref>CDC. Hepatitis surveillance. Report no. 61. Atlanta, GA: US Department of Health and Human Services, CDC. 2006</ref><ref name="pmid2166446">{{cite journal |author=Shaw FE, Shapiro CN, Welty TK, Dill W, Reddington J, Hadler SC |title=Hepatitis transmission among the Sioux Indians of South Dakota |journal=[[American Journal of Public Health]] |volume=80 |issue=9 |pages=1091–4 |year=1990 |month=September |pmid=2166446 |pmc=1404852 |doi= |url= |accessdate=2012-02-28}}</ref><ref name="pmid8376812">{{cite journal |author=Bulkow LR, Wainwright RB, McMahon BJ, Middaugh JP, Jenkerson SA, Margolis HS |title=Secular trends in hepatitis A virus infection among Alaska Natives |journal=[[The Journal of Infectious Diseases]] |volume=168 |issue=4 |pages=1017–20 |year=1993 |month=October |pmid=8376812 |doi= |url=http://www.jid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=8376812 |accessdate=2012-02-28}}</ref><ref name="pmid15249305">{{cite journal |author=Bialek SR, Thoroughman DA, Hu D, Simard EP, Chattin J, Cheek J, Bell BP |title=Hepatitis A incidence and hepatitis a vaccination among American Indians and Alaska Natives, 1990-2001 |journal=[[American Journal of Public Health]] |volume=94 |issue=6 |pages=996–1001 |year=2004 |month=June |pmid=15249305 |pmc=1448379 |doi= |url= |accessdate=2012-02-28}}</ref>
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| Since the 1960s, the highest hepatitis A rates and the majority of cases occurred in a limited number of states and counties concentrated in the western and southwestern United States.<ref name="pmid16014593">{{cite journal |author=Wasley A, Samandari T, Bell BP |title=Incidence of hepatitis A in the United States in the era of vaccination |journal=[[JAMA : the Journal of the American Medical Association]] |volume=294 |issue=2 |pages=194–201 |year=2005 |month=July |pmid=16014593 |doi=10.1001/jama.294.2.194 |url=http://jama.ama-assn.org/cgi/pmidlookup?view=long&pmid=16014593 |accessdate=2012-02-28}}</ref> Despite year-to-year fluctuations, rates in these areas consistently remained above the national average. In 11 states (Alaska, Arizona, California, Idaho, Nevada, New Mexico, Oklahoma, Oregon, South Dakota, Utah, and Washington) with consistently elevated rates, representing 22% of the U.S. population, average annual hepatitis A incidence was >20 cases per 100,000 during 1987-1997 (twice the national average of approximately 10 cases per 100,000 population); cases among residents of these states accounted for an average of 50% of reported cases.<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4812a1.htm CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1999;48(No. RR-12):1-37]</ref> An additional 18% of cases occurred among residents of six states (Arkansas, Colorado, Missouri, Montana, Texas, and Wyoming) with average annual rates above (but less than twice) the national average during this time.
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| Approximately 31% of the U.S. population had serologic evidence of previous HAV infection, when measured in the Third National Health and Nutrition Examination Survey (NHANES-III) conducted during 1988-1994 (50). Anti-HAV prevalence varied directly with age: among persons aged 6-11 years, prevalence was 9%; 20--29 years, 19%; 40--49 years, 33%; and >70 years, 75%. Age-adjusted anti-HAV prevalence was considerably higher among Mexican-American (70%) compared with black (39%) and white (23%) participants, and among foreign-born (69%) compared with U.S.-born (25%) participants.
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| ====Sources of Infection====
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| In the prevaccine era, the majority of U.S. cases of hepatitis A resulted from person-to-person transmission of HAV during communitywide outbreaks.<ref name="pmid9815207">{{cite journal |author=Bell BP, Shapiro CN, Alter MJ, Moyer LA, Judson FN, Mottram K, Fleenor M, Ryder PL, Margolis HS |title=The diverse patterns of hepatitis A epidemiology in the United States-implications for vaccination strategies |journal=[[The Journal of Infectious Diseases]] |volume=178 |issue=6 |pages=1579–84 |year=1998 |month=December |pmid=9815207 |doi= |url=http://www.jid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=9815207 |accessdate=2012-02-28}}</ref><ref>CDC. Communitywide outbreaks of hepatitis A. Hepatitis surveillance. Report no. 51. Atlanta, GA: US Department of Health and Human Services, CDC; 1987:6-8.</ref> The most frequently reported source of infection (in 12%-26% of cases) was household or sexual contact with a person with hepatitis A.<ref name="pmid1476001">{{cite journal |author=Shapiro CN, Coleman PJ, McQuillan GM, Alter MJ, Margolis HS |title=Epidemiology of hepatitis A: seroepidemiology and risk groups in the USA |journal=[[Vaccine]] |volume=10 Suppl 1 |issue= |pages=S59–62 |year=1992 |pmid=1476001 |doi= |url= |accessdate=2012-02-28}}</ref> Cyclic outbreaks occurred among users of injection and noninjection drugs and among men who have sex with men (MSM),<ref name="pmid12696002">{{cite journal |author=Cotter SM, Sansom S, Long T, Koch E, Kellerman S, Smith F, Averhoff F, Bell BP |title=Outbreak of hepatitis A among men who have sex with men: implications for hepatitis A vaccination strategies |journal=[[The Journal of Infectious Diseases]] |volume=187 |issue=8 |pages=1235–40 |year=2003 |month=April |pmid=12696002 |doi=10.1086/374057 |url=http://www.jid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=12696002 |accessdate=2012-02-28}}</ref><ref name="pmid2929804">{{cite journal |author=Harkess J, Gildon B, Istre GR |title=Outbreaks of hepatitis A among illicit drug users, Oklahoma, 1984-87 |journal=[[American Journal of Public Health]] |volume=79 |issue=4 |pages=463–6 |year=1989 |month=April |pmid=2929804 |pmc=1349976 |doi= |url= |accessdate=2012-02-28}}</ref><ref name="pmid3140269">{{cite journal |author=Schade CP, Komorwska D |title=Continuing outbreak of hepatitis A linked with intravenous drug abuse in Multnomah County |journal=[[Public Health Reports (Washington, D.C. : 1974)]] |volume=103 |issue=5 |pages=452–9 |year=1988 |pmid=3140269 |pmc=1478131 |doi= |url= |accessdate=2012-02-28}}</ref><ref name="pmid10358687">{{cite journal |author=Hutin YJ, Bell BP, Marshall KL, Schaben CP, Dart M, Quinlisk MP, Shapiro CN |title=Identifying target groups for a potential vaccination program during a hepatitis A communitywide outbreak |journal=[[American Journal of Public Health]] |volume=89 |issue=6 |pages=918–21 |year=1999 |month=June |pmid=10358687 |pmc=1508638 |doi= |url= |accessdate=2012-02-28}}</ref><ref name="pmid15620475">{{cite journal |author=Vong S, Fiore AE, Haight DO, Li J, Borgsmiller N, Kuhnert W, Pinero F, Boaz K, Badsgard T, Mancini C, Nainan OV, Wiersma S, Bell BP |title=Vaccination in the county jail as a strategy to reach high risk adults during a community-based hepatitis A outbreak among methamphetamine drug users |journal=[[Vaccine]] |volume=23 |issue=8 |pages=1021–8 |year=2005 |month=January |pmid=15620475 |doi=10.1016/j.vaccine.2004.07.038 |url=http://linkinghub.elsevier.com/retrieve/pii/S0264-410X(04)00622-X |accessdate=2012-02-28}}</ref> and up to 15% of nationally reported cases occurred among persons reporting one or more of these behaviors. Other potential sources of infection (e.g., international travel and recognized foodborne outbreaks) were reported among 3%--6% of cases.<ref name="pmid1476001">{{cite journal |author=Shapiro CN, Coleman PJ, McQuillan GM, Alter MJ, Margolis HS |title=Epidemiology of hepatitis A: seroepidemiology and risk groups in the USA |journal=[[Vaccine]] |volume=10 Suppl 1 |issue= |pages=S59–62 |year=1992 |pmid=1476001 |doi= |url= |accessdate=2012-02-28}}</ref> For approximately 50% of persons with hepatitis A, no source was identified for their infection. | |
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| ===Vaccine Era===
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| With the licensure of inactivated hepatitis A vaccines by the Food and Drug Administration (FDA) during 1995-1996, hepatitis A became a disease that was not only common but also vaccine-preventable. Since 1996, and particularly since ACIP's 1999 recommendations for routine vaccination of children living in areas with consistently elevated hepatitis A rates, national hepatitis A rates have declined sharply.<ref name="pmid16014593">{{cite journal |author=Wasley A, Samandari T, Bell BP |title=Incidence of hepatitis A in the United States in the era of vaccination |journal=[[JAMA : the Journal of the American Medical Association]] |volume=294 |issue=2 |pages=194–201 |year=2005 |month=July |pmid=16014593 |doi=10.1001/jama.294.2.194 |url=http://jama.ama-assn.org/cgi/pmidlookup?view=long&pmid=16014593 |accessdate=2012-02-28}}</ref> The 1999 recommendations called for routine vaccination of children living in states and communities in which the average hepatitis A rate during a baseline period of 1987-1997 was >20 cases per 100,000 population, approximately twice the national average, and for consideration of hepatitis A vaccination of children in those states and communities in which the average rate during the baseline period was at least the national average.<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4812a1.htm CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1999;48(No. RR-12):1-37.]</ref>
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| In 2004, a total of 5,683 cases (rate: 1.9 cases per 100,000 population) were reported, representing an estimated 24,000 acute clinical cases when underreporting is taken into account. This rate was the lowest ever recorded and was 79% lower than the previously recorded low in 1992.<ref>CDC. Hepatitis surveillance. Report no. 61. Atlanta, GA: US Department of Health and Human Services, CDC. 2006</ref> This decline is reflected in other fundamental shifts in hepatitis A epidemiology.
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| ====Communitywide Epidemics====
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| During communitywide epidemics, infection was transmitted from person to person in households and extended family settings. These epidemics typically spread throughout the community, and no single risk factor or risk group could be identified that accounted for the majority of cases.<ref name="pmid9815207">{{cite journal |author=Bell BP, Shapiro CN, Alter MJ, Moyer LA, Judson FN, Mottram K, Fleenor M, Ryder PL, Margolis HS |title=The diverse patterns of hepatitis A epidemiology in the United States-implications for vaccination strategies |journal=[[The Journal of Infectious Diseases]] |volume=178 |issue=6 |pages=1579–84 |year=1998 |month=December |pmid=9815207 |doi= |url=http://www.jid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=9815207 |accessdate=2012-02-28}}</ref> Once initiated, epidemics often persisted for 1--2 years and proved difficult to control.<ref name="pmid3706276">{{cite journal |author=Shaw FE, Sudman JH, Smith SM, Williams DL, Kapell LA, Hadler SC, Halpin TJ, Maynard JE |title=A Community-wide epidemic of hepatitis A in Ohio |journal=[[American Journal of Epidemiology]] |volume=123 |issue=6 |pages=1057–65 |year=1986 |month=June |pmid=3706276 |doi= |url= |accessdate=2012-02-28}}</ref><ref name="pmid9770153">{{cite journal |author=Craig AS, Sockwell DC, Schaffner W, Moore WL, Skinner JT, Williams IT, Shaw FE, Shapiro CN, Bell BP |title=Use of hepatitis A vaccine in a community-wide outbreak of hepatitis A |journal=[[Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America]] |volume=27 |issue=3 |pages=531–5 |year=1998 |month=September |pmid=9770153 |doi= |url=http://www.cid.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=9770153 |accessdate=2012-02-28}}</ref> Because children often have unrecognized or asymptomatic infection, they played a key role in sustaining HAV transmission during these epidemics.
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| ==References== | | ==References== |
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| {{Reflist|2}} | | {{Reflist|2}} |
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| [[Category:Needs content]] | | [[Category:Needs content]] |
| [[Category:Foodborne illnesses]] | | [[Category:Foodborne illnesses]] |
| [[Category:hepatitis|A]] | | [[Category:Hepatitis|A]] |
| [[Category:Picornaviruses]] | | [[Category:Picornaviruses]] |
| [[Category:Viral diseases]] | | [[Category:Viral diseases]] |
| [[Category:Mature chapter]] | | [[Category:Mature chapter]] |
| | [[Category:Disease]] |
| | [[Category:Emergency mdicine]] |
| | [[Category:Up-To-Date]] |
| [[Category:Infectious disease]] | | [[Category:Infectious disease]] |
| [[Category:Disease]] | | [[Category:Hepatology]] |
| | | [[Category:Gastroenterology]] |
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