Viral Hepatitis - part 8 pdf

Hepatitis E as a zoonotic disease 623 66 Purcell RH, Emerson SU. Hepatitis E virus. In: Knipe DM, Howley PM, Griffi n DE et al., eds. Fields Virology, 4th edn. Phil- adelphia: Lippincott Williams and Wilkins, 2001:3051–61. 67 Meng XJ. Swine hepatitis E virus: cross-species infection and risk in xenotransplantation. Curr Top Microbiol Immunol 2003;278:185–216. 68 Emerson SU, Purcell RH. Hepatitis E virus. Rev Med Virol 2003;13:145–54. 69 Schlauder GG, Mushahwar IK. Genetic heterogeneity of hepa- titis E virus. J Med Virol 2001;65:282–92. 70 Williams TP, Kasorndorkbua C, Halbur PG et al. Evidence of extrahepatic sites of replication of the hepatitis E virus in a swine model. J Clin Microbiol 2001;39:3040–6. 71 Kasorndorkbua C, Halbur PG, Thomas PJ et al. Use of a swine bioassay and a RT-PCR assay to assess the risk of transmission of swine hepatitis E virus in pigs. J Virol Methods 2002;101:71– 8. 72 Choi C, Chae C. Localization of swine hepatitis E virus in liver and extrahepatic tissues from naturally infected pigs by in situ hybridization. J Hepatol 2003;38:827–32. 73 Takahashi M, Nishizawa T, Miyajima H et al. Swine hepatitis E virus strains in Japan form four phylogenetic clusters com- parable with those of Japanese isolates of human hepatitis E virus. J Gen Virol 2003;84:851–62. 74 Chandler JD, Riddell MA, Li F et al. Serological evidence for swine hepatitis E virus infection in Australian pig herds. Vet Microbiol 1999;68:95–105. 75 Yoo D, Willson P, Pei Y et al. Prevalence of hepatitis E virus antibodies in Canadian swine herds and identifi cation of a novel variant of swine hepatitis E virus. Clin Diagn Lab Immu- nol 2001;8:1213–19. 76 Choi IS, Kwon HJ, Shin NR, Yoo HS. Identifi cation of swine hepatitis E virus (HEV) and prevalence of anti-HEV antibod- ies in swine and human populations in Korea. J Clin Microbiol 2003;41:3602–8. 77 Garkavenko O, Obriadina A, Meng J et al. Detection and char- acterization of swine hepatitis E virus in New Zealand. J Med Virol 2001;65:525–9. 78 Arankalle VA, Chobe LP, Joshi MV et al. Human and swine hepatitis E viruses from Western India belong to different gen- otypes. J Hepatol 2002;36:417–25. 79 Arankalle VA, Chobe LP, Walimbe AM et al. Swine HEV in- fection in south India and phylogenetic analysis (1985–1999). J Med Virol 2003;69:391–6. 80 Huang FF, Haqshenas G, Guenette DK et al. Detection by reverse transcription-PCR and genetic characterization of fi eld isolates of swine hepatitis E virus from pigs in differ- ent geographic regions of the United States. J Clin Microbiol 2002;40:1326–32. 81 Pei Y, Yoo D. Genetic characterization and sequence heteroge- neity of a Canadian isolate of Swine hepatitis E virus. J Clin Microbiol 2002;40:4021–9. 82 Krawczynski K, Kamili S, Aggarwal R. Global epidemiology and medical aspects of hepatitis E. Forum (Genova) 2001;11:166– 79. 83 Aggarwal R, Krawczynski K. Hepatitis E: an overview and recent advances in clinical and laboratory research. J Gastroen- terol Hepatol 2000;15:9–20. 84 Balayan MS. Epidemiology of hepatitis E virus infection. J Vi- ral Hepat 1997;4:155–65. 85 Harrison TJ. Hepatitis E virus – an update. Liver 1999;19:171– 6. 86 Thomas DL, Yarbough PO, Vlahov D et al. Seroreactivity to hepatitis E virus in areas where the disease is not endemic. J Clin Microbiol 1997;35:1244–7. 87 Mast EE, Kuramoto IK, Favorov MO et al. Prevalence of and risk factors for antibody to hepatitis E virus seroreactiv- ity among blood donors in Northern California. J Infect Dis 1997;176:34–40. 88 McCrudden R, O’Connell S, Farrant T et al. Sporadic acute hepatitis E in the United Kingdom: an underdiagnosed phe- nomenon? Gut 2000;46:732–3. 89 Aggarwal R, Kamili S, Spelbring J et al. Experimental stud- ies on subclinical hepatitis E virus infection in cynomolgus macaques. J Infect Dis 2001;184:1380–5. 90 Van Cuyck-Gandre H, Zhang HY, Tsarev SA et al. Short report: phylogenetically distinct hepatitis E viruses in Pakistan. Am J Trop Med Hyg 2000;62:187–9. 91 Mast EE, Alter MJ, Holland PV, Purcell RH. Evaluation of assays for antibody to hepatitis E virus by a serum panel. Hepatitis E Virus Antibody Serum Panel Evaluation Group. Hepatology 1998;27:857–61. 92 Crerar SK, Cross GM. Epidemiological and clinical investiga- tions into big liver and spleen disease of broiler breeder hens. Aust Vet J 1994;71:410–13. 93 Huang FF, Sun ZF, Emerson SU et al. Determination and analy- ses of the complete genomic sequence of avian hepatitis E vi- rus (avian HEV) and attempts to experimentally infect rhesus monkeys with avian HEV. J Gen Virol 2004;85(Pt 6):1609–18. 94 Smith JL. A review of hepatitis E virus. J Food Prot 2001;64:572– 86. 95 Halbur PG, Kasorndorkbua C, Meng XJ. Hepatitis E virus: zoonotic threat or harmless commensal of pigs. Proc 11th Ann Swine Dis Conf for Swine Vet. Iowa: Ames, 2003:34–9. 96 Karetnyi YV, Moyer N, Gilchrist MJR, Naides SJ. Swine hepa- titis E virus contamination in hog operation waste streams. An emerging infection? Workshop on the Effects of Animal Feed- ing Operations on Hydrologic Resources and the Environment. United States Geological Survey Animal Feedlot Operations, Fort Collins, CO, 3 August 1999. 97 Vaidya SR, Tilekar BN, Walimbe AM, Arankalle VA. Increased risk of hepatitis E in sewage workers from India. J Occup Envi- ron Med 2003;45:1167–70. 98 Jothikumar N, Aparna K, Kamatchiammal S et al. Detection of hepatitis E virus in raw and treated wastewater with the polymerase chain reaction. Appl Environ Microbiol 1993;59:2558– 62. 99 Cacopardo B, Russo R, Preiser W et al. Acute hepatitis E in Ca- tania (eastern Sicily) 1980–1994. The role of hepatitis E virus. Infection 1997;25:313–16. 100 Mechnik L, Bergman N, Attali M et al. Acute hepatitis E virus infection presenting as a prolonged cholestatic jaundice. J Clin Gastroenterol 2001;33:421–2. 101 Kasorndorkbua C, Thacker BJ, Halbur PG et al. Experimental infection of pregnant gilts with swine hepatitis E virus. Can J Vet Res 2003;67:303–6. 1405130059_4_040.indd 6231405130059_4_040.indd 623 30/03/2005 12:43:5530/03/2005 12:43:55 624 Chapter 41 Epidemiology, clinical and pathologic features, diagnosis, and experimental models Kris Krawczynski, Rakesh Aggarwal, Saleem Kamili Hepatitis E, previously known as enterically transmit- ted non-A, non-B hepatitis, was fi rst recognized as a dis- tinct clinical entity in the 1980s, when sera from persons affected during a large waterborne epidemic of acute hepatitis during 1955–1956 in Delhi, India and another epidemic in Kashmir, India tested negative for serologi- cal markers of acute hepatitis A and B. 1–3 The occurrence of the fi rst recorded epidemic of hepatitis E as late as 1955 and the infrequency of this disease in developed countries suggest that hepatitis E is a new, emerging in- fectious disease. However, several epidemics of enteri- cally transmitted hepatitis with epidemiologic features resembling those of hepatitis E outbreaks occurred in Europe and the United States in the 18th and 19th Cen- turies. 4,5 It is conceivable, therefore, that hepatitis E virus (HEV) infection may have been more widespread in the past and has only recently become restricted to certain geographic regions, mostly underdeveloped with poor environmental sanitation. Epidemiology Hepatitis E in disease-endemic regions Regions of the world can be considered as hepatitis E disease-endemic or non-endemic based on the periodic occurrence of disease outbreaks. Several large epidemics of hepatitis E, characterized by the epidemiologic fea- tures summarized in Table 41.1, have been observed in the Indian subcontinent, and in developing countries of south-east and central Asia. 1,2,6,7 Outbreaks of hepatitis E have been observed in the Middle East, and northern and western parts of Africa. In North America (Mexico), two small outbreaks were reported in the year 1986– 1987 (Fig. 41.1). 8,9 The hepatitis E outbreaks in HEV-en- demic regions are large, 1,2,6,7 frequently affecting several hundred to several thousand persons. Their time-course varies from single-peaked outbreaks lasting a few weeks to prolonged, multi-peaked epidemics lasting for over a year. The outbreaks recur with a periodicity of 5–10 years. The exact reason for this phenomenon remains unknown. The outbreaks frequently follow heavy rain- fall and fl oods, but sometimes may occur in hot and dry summer months. In areas where hepatitis E outbreaks occur, HEV in- fection accounts for a substantial proportion of acute sporadic hepatitis in both children and adults. In India, HEV infection accounts for 50–70% of all patients with sporadic viral hepatitis. 10,11 Demographic and clinical features of patients with sporadic hepatitis E (age distri- bution, severity and duration of illness, worse prognosis among pregnant women and absence of chronic seque- lae) closely resemble those of epidemic hepatitis E. 12–14 Transmission, routes of spread and attack rates in disease-endemic regions The faecal-oral route is the predominant mode of trans- mission of epidemic HEV infection. Most reported outbreaks have been related to consumption of fae- Table 41.1 Epidemiologic features of hepatitis E Large outbreaks in developing countries affecting several thousand persons Sporadic hepatitis cases frequent in disease-endemic areas Sporadic hepatitis cases uncommon in non-endemic areas (occur mainly among travellers to disease-endemic areas) Faecal-oral transmission (usually through contaminated water) Highest attack rate among young adults aged 15–40 years, with relative sparing of children Insignifi cant person-to-person transmission No evidence of parenteral or sexual transmission Mother-to-newborn (transplacental) transmission probable High mortality rate (15–25%) among pregnant women, especially those in third trimester 1405130059_4_041.indd 6241405130059_4_041.indd 624 30/03/2005 12:44:2730/03/2005 12:44:27 Epidemiology, clinical and pathologic features, diagnosis, and experimental models 625 cally contaminated drinking water. 1,2,6,15 The outbreaks frequently follow heavy rains and fl oods, when water sources become contaminated. 2,15 Some epidemics have occurred in hot summer months, when the diminution of water fl ow rate in rivers and streams may increase the concentration of contaminants, thereby increasing the risk of infection. 6,16 In some outbreaks, contamination of water occurred in leaky water pipes with intermittent water supply passing through areas contaminated with sewage, where a negative pressure in the pipes during periods of no fl ow leads to suction of contaminants. In south-east Asia, disposal of human excreta into rivers, and use of the same river water for drinking, cooking and personal hygiene has been shown to be associated with recurrent epidemics, 17 possibly through continuous existence of conditions that allow faecal contamination of water. In some small outbreaks of HEV infection in China that occurred after community feasts, food-borne transmission has been postulated. 7 However, these re- ports did not include any control data or results of sero- logic investigations. During hepatitis E outbreaks, person-to-person trans- mission of HEV appears to be distinctly uncommon. 2,18 Such transmission is also uncommon from patients with sporadic HEV infection in disease-endemic regions. 19 The mode of transmission responsible for sporadic hepatitis E thus is unclear. Secondary attack rates among house- hold contacts of patients with hepatitis E cases are only 0.7–2.2% 2,20 in contrast, 50–75% of susceptible household contacts of patients with hepatitis A become infected. 21 Even when multiple cases occur among members of a family, this is related to exposure to a common source of contaminated water rather than to person-to-person spread. 18 Presumed nosocomial spread of HEV has been reported in South Africa, where three health-care work- ers who treated a patient with fulminant hepatitis E de- veloped acute hepatitis 6 weeks later. 22 Vertical transmission of HEV infection from mother to infant has been reported. In one study, fi ve of six ba- bies born to mothers with either acute uncomplicated or fulminant hepatitis E in the third trimester of preg- nancy had HEV RNA in their blood samples taken at birth, suggesting transplacental transmission of infec- tion. 23 However, in an experimental study, HEV-infected pregnant rhesus monkeys failed to transmit the virus to their offspring. 24 Until recently, HEV was believed not to be transmitted through transfusion of blood or blood products because individuals with symptomatic HEV infection are unlikely to donate blood and HEV viraemia does not become chronic. Accordingly, anti- HEV antibody prevalence rates among patients with haemophilia and thalassaemia, who frequently receive transfusions, and among intravenous drug users are not higher than those in the general population. 25 However, a recent study has documented the presence of HEV vi- raemia among healthy blood donors and transmission of this infection to transfusion recipients in a disease- endemic region. 26 During hepatitis E outbreaks, overall attack rates range from 1% to 15%, being much higher among adults (3–30%) than those among children below 14 years of age (0.2–10%). 1,6,15,27 In most reports, the male-to-female ratio among cases has varied from 1:1 to 4:1; it is un- clear whether this refl ects greater frequency of exposure among men or a true difference in susceptibility. The outbreaks are characterized by a particularly high attack Figure 41.1 Geographical distribution of hepatitis E. Endemic zone High endemic zone Non-endemic zone 1405130059_4_041.indd 6251405130059_4_041.indd 625 30/03/2005 12:44:3130/03/2005 12:44:31 Chapter 41626 rate and mortality among pregnant women. 1,2,6,7 In an epidemic in Kashmir, India, attack rates among those in the fi rst, second and third trimesters were 8.8%, 19.4% and 18.6%, respectively, as compared with 2.1% among non-pregnant women and 2.8% among men. 28 Hepatitis E in disease non-endemic regions In non-endemic regions, where outbreaks have not been reported, the disease accounts for <1% of reported cases of acute viral hepatitis, and indigenous transmission of hepatitis E in these regions appears to be rather rare. A few isolated sporadic cases have been described from the USA, countries in Europe (including Austria, Spain, Italy, Greece and Turkey), 29–33 developed countries in Asia (Japan, Taiwan, Hong Kong), 34–36 South America (Argentina) 37 and Africa (Egypt, Senegal and Tunisia). 38,39 Most of the sporadic cases in non-endemic regions have been associated with travel to HEV-endemic regions, 40,41 although some cases, including two cases in the USA, 42– 44 have been reported among persons with no history of travel to disease-endemic countries. Recent Japanese cases have been associated with consumption of inad- equately cooked animal meat that contained HEV. 45 HEV molecular epidemiology and seroprevalence rates Nucleotide sequences have been determined for HEV isolates from disease-endemic countries and from non- endemic regions. Four genotypes of HEV have been proposed: genotype 1 comprises south-east and central Asian isolates from Burma, Pakistan, India and China; genotype 2 comprises a single Mexican isolate; genotype 3 comprises US human and swine isolates; and geno- type 4 comprises new Chinese isolates. 37,46–48 A variant strain of HEV has also been reported from tissue and faecal specimens of wild-trapped rodents from Nepal. 49 More recently, a novel virus related to HEV was identi- fi ed in chickens with the hepatitis-hepatosplenomegaly syndrome in the United States. Genomic sequence anal- ysis of the avian HEV in the helicase region reveals its partial identity (58–60% in amino acid and nucleotide sequences) to other HEV strains. 50 Comparison of nucle- otide sequences in HEV isolates derived from patients affected during an outbreak in the disease-endemic re- gion showed a high degree of identity. 51 Clinical and ep- idemiological differences have been observed between HEV strains within the same genotype. 52 It has been suggested that different strains may co-exist in a single population, some causing epidemic disease and others sporadic disease. 52 Anti-HEV IgG antibody has been found in healthy subjects living in all geographical areas, although its prevalence differs signifi cantly in various countries. In disease-endemic areas of Asia and Africa, the prevalence of antibody to HEV in documented endemic regions has been much lower than expected (3–26%), and the preva- lence of such antibody in non-endemic regions has been much higher than anticipated (1–5%). In most disease- endemic areas, anti-HEV has been detected in up to 5% of children younger than 10 years of age. This proportion increases to 10–40% among adults older than 25 years of age. 53,54 However, in a report from India, anti-HEV anti- bodies were detected in >60% of children below the age of 5 years. 55 The differences between different disease- endemic areas may be related to varying epidemiologi- cal conditions in different geographic areas, differences in diagnostic techniques used, or both. In developed countries of Europe and North America, 1–5% of the population has anti-HEV. 56,57 This range ap- pears to be relatively high compared with the low rate of clinically evident hepatitis E disease in these areas. Several assays were applied to both acute hepatitis E and population studies for detection of IgG anti-HEV. In a direct comparison using a panel of coded sera, 58 sen- sitivity rates of these assays were found to vary widely from 17% to 100%, and concordance rates among reac- tive sera ranged from none to 89% (median 32%). In another study, in which two different serologic tests for anti-HEV were used, it was found that concordance be- tween the two tests was only 27%. 59 It remains unclear whether the anti-HEV seroreactivity in non-endemic ar- eas refl ects subclinical and/or anicteric HEV infection, serologic cross-reactivity with other agents, false-posi- tivity of serologic tests, transmission of infection by con- tact with various animal reservoirs (swine, rodents), or a combination of all these factors. Reservoirs of HEV In disease-endemic areas, the source of HEV for maintaining the disease in a population has not been completely determined, and the existence of many res- ervoirs has been postulated. Based on data from a small group of patients, it has been suggested that protracted viraemia and prolonged faecal shedding of HEV may have a role in the continuous contamination of sew- age. 60 However, recent data generated from studies on a larger number of patients showed that the period of viral shedding in the faeces is much shorter. 61 Subclini- cal HEV infections that maintain the presence of the virus in a population during inter-epidemic periods may be a potential reservoir of HEV in disease-endemic regions. In the experimental model of HEV infection in cynomolgus macaques, which faithfully reproduces HEV infection in humans, animals with HEV infection but without biochemical evidence of liver injury ex- creted large amounts of HEV infectious to HEV-naïve animals. 62 Shedding of large quantities of viable virus 1405130059_4_041.indd 6261405130059_4_041.indd 626 30/03/2005 12:44:3130/03/2005 12:44:31 Epidemiology, clinical and pathologic features, diagnosis, and experimental models 627 during subclinical infection in humans may, therefore, represent a potential reservoir of HEV during inter-epi- demic periods. Existence of a reservoir of HEV in the form of subclinical infection in a population could be similar to the continuous presence of polio virus in are- as where that infection used to be endemic. 63 HEV shed by individuals with subclinical infection may contami- nate drinking water supplies during periods of fl ooding of river systems, leading to large outbreaks. However, more epidemiologic and laboratory data are needed to confi rm the existence of continuous subclinical circula- tion of HEV in disease-endemic areas. A zoonotic reservoir of HEV has also been suggested, based primarily on anti-HEV reactivity of serum speci- mens obtained from various animal species and on frag- mentary genomic sequence data. Anti-HEV antibodies have been detected in pigs in several endemic regions such as Nepal, China, India and Thailand, and in sev- eral non-endemic regions including the USA, Canada, Korea, Taiwan, Spain and Australia. 64–69 Anti-HEV has also been detected in chicken, cattle, sheep and rodents in several disease-endemic regions 64 and in 44–90% of rats in different parts of the USA. 70–72 The discovery of a swine HEV and the demonstration of a genetic rela- tionship of animal HEV strains from the USA, Taiwan and Spain with human isolates from these respective geographical areas may support this hypothesis. 29,44,73 Nucleotide sequence homology between HEV RNA isolated from some Japanese hepatitis E patients and those from the undercooked animal meat that they had eaten may also support animal-to-human transmis- sion. 45 Although the infrequent occurrence of clinically overt HEV infection in non-endemic areas with a high prevalence of anti-HEV among pigs and rats may de- pend on better sanitation, good water quality, and at- tention to personal hygiene, it is inconsistent with the hypothesis of universal zoonotic origin of hepatitis E. Moreover, Asian and Mexican strains of HEV associat- ed with large outbreaks of hepatitis E have failed to in- duce infection in experimentally inoculated pigs. 42,74,75 More molecular data are needed before the zoonotic reservoir can be implicated as playing a major role in the epidemiology of hepatitis E, especially given that genomic sequences of HEV strains isolated from ani- mals varied from those found in humans in a hepatitis E-endemic region in India. 76 In summary, current epidemiologic data indicate that large outbreaks, sporadic hepatitis E cases and subclinical HEV infection in the disease-endemic re- gions originate from an environmental, human, or yet to be identifi ed animal HEV reservoir. Poor general sanitation, contamination of drinking water supplies and lack of attention to personal hygiene are important factors contributing to the spread of infection in these areas. Clinical and pathological features The incubation period of hepatitis E is variable and has ranged from 2 to 10 weeks during waterborne outbreaks with a short and well-defi ned period of water contami- nation. 2,77 Clinical manifestations of HEV infection are similar to those of acute infection with other hepatitis viruses and encompass a wide spectrum of symptoms (Table 41.2). Acute icteric hepatitis is the most common recognizable form of illness associated with HEV infec- tion. This illness is usually insidious in onset and has an initial prodromal phase lasting about 1–4 days, with a variable combination of fl u-like symptoms, fever, mild chills, abdominal pain, anorexia, nausea, aversion to smoking, vomiting, clay-coloured stools, dark or tea- coloured urine, diarrhoea, arthralgias, asthenia and a transient macular skin rash (Table 41.3). 1,7,8,78–81 These symptoms are followed in a few days by the appearance of jaundice. The onset of the icteric phase is frequently heralded by darkening of the urine and may be accom- panied by lightening of stool colour or itching. Physi- cal examination reveals jaundice and a mildly enlarged, soft and slightly tender liver. A soft splenomegaly is ob- served in nearly one-quarter of patients. 81 Laboratory test abnormalities include bilirubinuria, variable degree of rise in serum bilirubin (predomi- nantly conjugated), marked elevation in serum alanine aminotransferase (ALT), aspartate aminotransferase and gamma-glutamyl transferase activities, and a mild rise in serum alkaline phosphatase activity. An eleva- tion of aminotransferase levels may precede the onset of symptoms by as long as 10 days and reaches a peak by the end of the fi rst week. As the illness subsides, ami- notransferase levels decrease signifi cantly, followed by diminution in serum bilirubin level, and liver function test values usually return to normal by 6 weeks. 81 The magnitude of transaminase elevation does not correlate well with the severity of liver injury. Some patients show Table 41.2 Clinical features of hepatitis E Incubation period 2–10 weeks Variable clinical manifestations including: icteric hepatitis severe hepatitis leading to fulminant hepatic failure anicteric hepatitis inapparent, asymptomatic infection Clinical illness similar to other viral hepatitis (except among pregnant women) Milder illness in children Low mortality rate (0.07–0.6%) High attack rate in pregnant women, particularly those in second and third trimesters High mortality (15–25%) among pregnant women No relation with chronic hepatitis, cirrhosis or hepatocellular carcinoma 1405130059_4_041.indd 6271405130059_4_041.indd 627 30/03/2005 12:44:3130/03/2005 12:44:31 Chapter 41628 mild leukopenia and relative lymphocytosis. The illness is usually self-limiting and typically lasts 1–4 weeks. 80,81 Histopathological features of hepatitis E are similar to those of other forms of acute hepatitis, such as the pres- ence of ballooned hepatocytes and acidophilic bodies, and focal and confl uent hepatocyte necrosis with col- lapse and condensation of the underlying reticulum. Nearly half of hepatitis E patients have cholestatic hepa- titis, which is characterized by canalicular bile stasis and gland-like transformation of parenchymal cells. In these patients, degenerative changes in hepatocytes are less marked and polymorphonuclear infi ltration is promi- nent. 82 In both forms, lobules and enlarged portal tracts show infl ammatory infi ltration. No evidence of chronic hepatitis or cirrhosis has been detected among patients followed up clinically and with liver biopsies after acute hepatitis E. 9,82,83 A few pa- tients, however, have a prolonged course with marked cholestasis (cholestatic hepatitis), including persistent jaundice and prominent itching. In these cases, labora- tory tests show elevations in alkaline phosphatase and bilirubin levels even after transaminase levels have re- turned to normal. The prognosis is good, as jaundice fi - nally resolves spontaneously after 2–6 months. HEV-infected individuals may develop non-specifi c symptoms, resembling those of an acute viral febrile ill- ness without jaundice (anicteric hepatitis). In its most benign form, HEV infection is entirely inapparent and asymptomatic, and passes unnoticed. The exact frequen- cies of asymptomatic infection and of anicteric hepatitis are not known, although these probably far exceed that of icteric disease. In a small proportion of patients, disease is more se- vere and is associated with subacute (or late-onset) or fulminant hepatic failure (FHF) that can be rapidly fa- tal. In patients with severe liver injury, a large propor- tion of hepatocytes are affected, leading to submassive or massive necrosis and collapse of liver parenchyma. In disease-endemic regions, hepatitis E is an important cause of FHF. HEV infection (alone or in combination with other hepatitis viruses) in India was responsible for 62% of adult patients and 40% of children with sporadic FHF. 14,84,85 It has also been suggested that serious forms of hepatitis such as FHF and subacute hepatic failure may result from a combined infection with hepatitis B virus (HBV) and HEV. 12,86 In a recent study, Hamid et al. showed that hepatitis E infection in patients with pre- existing liver cirrhosis may lead to worsening of their clinical state. 87 The case-fatality rate in HEV infection has ranged from 0.5% to 4%. 20,88 However, these reports are based on hospital data and thus underestimate the total number of persons affected and may overestimate mortality. Population surveys during outbreaks report lower mor- tality rates varying from 0.07% to 0.6%. 6,81,88 In an epi- demic in Ethiopia, none of the 423 soldiers with icteric hepatitis developed FHF or died. 79 Pregnant women, particularly those in the second and third trimesters, are more frequently affected during hepatitis E outbreaks and have a worse outcome. Mortality rates among preg- nant women, especially those infected in the third tri- mester, have ranged between 5% and 25%. 15,20,27,28 FHF developed in 22.2% of the affected pregnant women, in comparison with 2.8% and 0% of affected men and non- pregnant women, respectively. 28 Frequency of abortions, stillbirths and neonatal deaths is also increased among pregnant women with HEV infection. 27 The reason for particularly severe liver damage in pregnant women with hepatitis E remains unknown. Diagnosis Detection of antibodies to HEV Historically, the fl uorescent antibody blocking assay (FA) was one of the earliest tests used for identifi ca- tion of antibodies that react with HEV antigen (HEVAg) identifi ed in hepatocytes of experimentally infected macaques. 89 Although the FA assay enabled the sero- logic identifi cation of HEV infection in various geo- graphic regions of the world, 89 it does not distinguish between recent and past infections, and requires liver Table 41.3 Clinical fi ndings in hepatitis E outbreaks Symptoms and signs Delhi, India 80 1956 (%) (n = 958) Accra, Ghana 78 1963 (%) (n = 136) Kashmir, India 1 1978 (%) (n = 275) Ethiopia 79 1989 (%) (n = 423) Xinjing, China 81 1986–88 (%) (n = 85) Jaundice 100 100 100 100 91 Malaise 95 100 95 Anorexia 66 95 79 100 69 Abdominal pain 63 37 41 82 55 Hepatomegaly 62 67 85 10 80 Nausea, vomiting 29 48 46 100 91 Fever 23 57 44 97 53 Pruritus 14 47 20 14 59 1405130059_4_041.indd 6281405130059_4_041.indd 628 30/03/2005 12:44:3130/03/2005 12:44:31 Epidemiology, clinical and pathologic features, diagnosis, and experimental models 629 tissue substrate that contains HEVAg from HEV-infect- ed primates. Enzyme immunoassays (EIAs) for the detection of IgM and IgG antibodies to HEV have been developed in several laboratories using recombinant HEV antigens expressed in Escherichia coli or insect cells, and synthetic peptides corresponding to immunogenic epitopes of HEV. 56,90–94 A synthetic gene encoding multiple linear immunodominant antigenic epitopes from ORF2 and ORF3 regions has been synthesized, expressed as a pro- tein and used in a solid-phase EIA. 95 Recently, a capture EIA format was shown to be more sensitive in detecting IgM, especially in the presence of high concentrations of IgG antibodies. 96 Although commercial kits for the detection of IgM and IgG anti-HEV are available from vendors in various countries, there is no commercial test for the detection of anti-HEV currently licensed for clin- ical use in the United States. The commercial kits and many ‘in-house’ EIAs use epitopes from two geographi- cally distinct HEV strains representing diverse antigenic domains as target antigens. 58 Antigenic domains that contain strong IgG and IgM antigenic epitopes have been identifi ed at the amino- and carboxyl-terminus of the ORF2 encoded protein 97 and have been shown to be more sensitive than ORF3-derived antigens, when used for detection of IgM and/or IgG anti-HEV. 98 A highly conserved conformational epitope mapped to 267 ami- no acids at the carboxyl-terminus of HEV ORF2 protein has been used in a sensitive and specifi c EIA format for the detection and quantifi cation of both acute and con- valescent phase HEV-specifi c IgG. 99 In clinical studies, determination of IgM anti-HEV is important for diagnosis of acute HEV infection, where- as the detection of IgG anti-HEV may be indicative of convalescent phase or past infection. During acute HEV infection, IgM anti-HEV appears in the early phase of clinical illness, preceding the IgG anti-HEV by a few days, and disappears over a 4–5-month period. 100 In one study, 100%, 50% and 40% of sera collected from pa- tients during various hepatitis E outbreaks 1–40 days, 3–4 months and 6–12 months after the onset of jaundice, respectively, tested positive for IgM anti-HEV. 91 In out- break settings, IgM anti-HEV has been detected in >90% of patient serum samples obtained within 1 week to 2 months after the onset of illness. 100 The IgG response appears shortly after the IgM response, and its titre in- creases throughout the acute phase into the convales- cent phase, and remains high from 1 to 4.5 years after the acute phase of illness. 56,100 In one study, anti-HEV was detected in 47% of persons 14 years after acute HEV infection, 101 but the exact duration of persistence of anti- HEV is not known. As EIAs are the most convenient, inexpensive and suitable assays for routine diagnosis of HEV infection as well as for sero-epidemiologic surveys, their sensitiv- ity and specifi city need to be improved. Currently used diagnostic assays for detection of anti-HEV have a wide range of sensitivity between 17% and 100%, when ap- plied to specimens from non-endemic areas. 58 Further studies on standardization of diagnostic anti-HEV tests may benefi t from the availability of a reference reagent for human anti-HEV serum developed by the Expert Committee on Biological Standardization of the World Health Organization. 102 Detection of HEV-like particles and HEV RNA The identifi cation of HEV in faeces, bile, blood and liver has been accomplished by the use of immune electron microscopy (IEM) with immunoglobulin preparations obtained from hepatitis E patients during early con- valescence. 103 Serologic cross-reactivity was observed between virus-like particles (VLPs) from epidemics of hepatitis E in Mexico, the former Soviet Union, Burma, Nepal, Pakistan, Sudan and Somalia, suggesting the ex- istence of a single viral serotype associated with these epidemics. 103,104 For routine diagnostic use, IEM is not practical because visualization and identifi cation of the virus is limited to samples with an abundance of VLPs. A more effi cient and a highly sensitive method for de- tection of HEV is the polymerase chain reaction (PCR). Several reverse transcriptase PCR (RT-PCR) assays have been developed for detecting genomic sequences of HEV in clinical and environmental samples. 29,105–109 HEV RNA sequences have been identifi ed in stool and serum sam- ples from patients and experimentally infected primates during the acute phase of hepatitis E. 61,110 Although various regions of sequence variation and conservation have been identifi ed in the HEV genome, there is no pre- ferred region selected for amplifi cation. Primers based on either the RNA-dependent RNA polymerase region in ORF1 or the ORF2 gene are most often used for am- plifi cation of HEV genomic fragments. HEV RNA can be detected in faeces of most patients with acute hepatitis E by RT-PCR during the initial few weeks. 61,111 In some patients, persistence of positive RT- PCR results for as long as 52 days has been reported. 60 HEV RNA has regularly been found in serum by RT-PCR in virtually all patients in the fi rst 2 weeks after the on- set of illness. 111 Prolonged periods of HEV RNA positiv- ity in serum ranging from 4 to 16 weeks have also been reported. 60,112 However, a recent, more extensive study did not fi nd any evidence of prolonged viral excretion or viraemia, 61 and no studies reported the presence of HEV in body fl uids other than serum. Generally, RT-PCR for HEV RNA is less suitable than serologic identifi cation of IgM anti-HEV for routine diagnosis of HEV infection be- cause HEV RNA may be degraded during faecal shed- ding of the virus, and the short viraemic phase usually occurs before the disease is clinically apparent. 1405130059_4_041.indd 6291405130059_4_041.indd 629 30/03/2005 12:44:3130/03/2005 12:44:31 Chapter 41630 Experimental HEV infection Experimental HEV infection in humans 112,113 and pri- mates 89,114–117 provided the most informative data on the pathogenetic events of the infection resulting from intragastric or intravenous administration of the virus. In 1983, a human volunteer ingested acute phase stool suspension from a water-borne epidemic of non-A hepa- titis in central Asia, and provided detailed clinical and biochemical data on the course of infection. 113 This ex- perimental infection led to the identifi cation of VLPs in stool specimens by immune electron microscopy with the use of anti-HEV antibodies obtained from the same individual during convalescence. The discovery of HEV allowed defi nition of the aetiological agent of the acute viral hepatitis transmitted by the faecal-oral route (hep- atitis E). In 1993, another human volunteer provided a set of clinical, virological and serological data that fur- ther characterized hepatitis E. 112 The incubation period of the disease in the human volunteers ranged from 4 to 5 weeks, HEV VLPs were found in stools 4–5 weeks af- ter exposure, and elevated enzyme activity reached the highest levels at 6–7 weeks after exposure. HEV RNA in serum was fi rst detected on day 22 post-exposure, a week before onset of disease on day 30, and anti-HEV antibody was detected 7 weeks post-infection. HEV in- fection in both volunteers resolved clinically with a re- turn of liver enzyme activity to the normal range. Experimental infection has successfully been at- tempted in non-human primates, such as chimpanzees, macaques (cynomolgus, rhesus and pigtail monkeys) and African green monkeys among the Old World spe- cies, and marmosets (tamarins) and owl monkeys among the New World species. 118 The levels of virus excretion, liver enzyme elevations and histopathologic changes in liver varied signifi cantly in these animals. 119 Experimen- tal, direct intrahepatic inoculation of chimpanzees and rhesus monkeys with RNA transcripts from full-length functional clones of HEV cDNA induced virological, pathological and serological characteristics typical of hepatitis E, and established a direct aetiological link be- tween the genetic material of HEV and the disease. 120 In intravenously inoculated cynomolgus macaques, the average incubation period for acute hepatitis E measured by a signifi cant increase of ALT activity val- ues is about 21 days. HEVAg was detected in hepato- cytes on about day 7 post-infection and was found in 70–90% of hepatocytes at the peak of viral replication (K. Krawczynski, unpublished data) that occurred be- fore or concurrently with the onset of ALT elevation and histopathological changes in the liver. 115,116 Both IgM and IgG anti-HEV have been detected in serum in assays us- ing immunoreactive epitopes of ORF2 and ORF3. The IgM antibody level decreases rather precipitously, reach- ing negligible levels in the early convalescent phase fol- lowed by high titres of IgG anti-HEV detected during convalescence. The antibodies have been observed as long as 10 years after onset of acute hepatitis E in chim- panzees experimentally infected with serum specimens derived from Tashkent, Pakistan and Mexico. 121 The variety of patterns of experimental infection in cynomolgus monkeys and chimpanzees resembles clini- cally overt or subclinical HEV infection in humans. In experimentally infected chimpanzees, the course of infection and disease measured by virus replication, antiviral humoral immune response and ALT activity was signifi cantly different among individual animals. 110 These differences in virological, immunological and pathological sequelae of infection may be explained by either individual host susceptibility to HEV infection or the size of the dose of infectious HEV. Inoculum titra- tion experiments in cynomolgus macaques have shown that animals infected with decreasing infectious doses had less marked clinical and pathological evidence of liver disease. Inoculation of the end-point dilution of an infectious inoculum (Mexico strain) was marked by se- roconversion to anti-HEV only. No evidence of the virus shedding in stools, HEVAg in the liver or liver pathol- ogy was found. These observations indicated that the clinical presentation of hepatitis E in a primate model depends on the size of the infectious dose, and the se- verity of infection seems to be directly related to the infectivity titre of the challenge inoculum. 62 The subclin- ical infection caused by the smaller infectious dose was associated with faecal viral excretion similar in magni- tude to that observed in the clinical form of the disease. The virus shed during subclinical infection was viable and capable of transmitting HEV infection to naïve cy- nomolgus macaques. 62 In summary, several elements of pathogenesis of HEV infection can be outlined based on data from human volunteers and patients, and those from experimentally infected animals (Fig. 41.2). The virus enters the host pri- marily through the oral route, but there have not been enough clinical and experimental data collected to doc- ument that HEV reaches the liver from the gastrointes- tinal tract through portal circulation. In experimentally infected primates, HEV RNA appears in serum, bile and faeces a few days before the onset of ALT rise. 110,114,116,122,123 HEVAg in hepatocytes has been detected simultane- ously with HEV identifi ed in bile and faeces during the second or third week after inoculation, before or con- currently with the onset of ALT elevation and morpho- logical changes in the liver. 89 These fi ndings suggest that HEV may be released from hepatocytes into bile during the initial, highly replicative phase of infection, before the occurrence of the most prominent histopathological changes in the liver. The onset of ALT elevation and the occurrence of pathological changes in the liver generally correspond to the detection of anti-HEV in serum and 1405130059_4_041.indd 6301405130059_4_041.indd 630 30/03/2005 12:44:3230/03/2005 12:44:32 Epidemiology, clinical and pathologic features, diagnosis, and experimental models 631 with decreasing levels of HEV antigen in hepatocytes. Lymphocytes infi ltrating liver in experimentally infected monkeys have a cytotoxic/suppression immunopheno- type. 124 Preliminary results of cellular immunity studies in hepatitis E patients indicate that lymphoproliferative responses to HEV peptides from ORF2 and ORF3 regions occur in patients with acute hepatitis E. 125 Concordance of pathological, virological and serological fi ndings in hepatitis E suggests that the pathomechanism of the disease may be immune-mediated rather than related to cytopathic effect of HEV. References 1 Khuroo MS. Study of an epidemic of non-A, non-B hepatitis: possibility of another human hepatitis virus distinct from post- transfusion non-A, non-B type. Am J Med 1980;68:818–23. 2 Vishwanathan R. Infectious hepatitis in Delhi (1955–56): a critical study: epidemiology. Indian J Med Res 1957;45(Suppl. 1):1–29. 3 Wong DC, Purcell RH, Sreenivasan MA, Prasad SR, Pavri KM. Epidemic and endemic hepatitis in India: evidence for a non- A, non-B hepatitis etiology. Lancet 1980;2:876–9. 4 Blumer GB. Infectious hepatitis in the United States. JAMA 1923;49:230–4. 5 Cockayne EA. Cattarhal jaundice, sporadic and epidemic, and its relation to acute yellow atrophy of the liver. Q J Med 1912;6:1. 6 Naik SR, Aggarwal R, Salunke PN, Mehrotra NN. A large waterborne viral hepatitis E epidemic in Kanpur, India. Bull WHO 1992;70:597–604. 7 Zhuang H. Hepatitis E and strategies for its control. In: Wen YM, Xu ZY, Melnick JL, eds. Viral hepatitis in China: problems and control strategies. Monogr Virol 1992;19:126–39. 8 Centers for Disease Control. Enterically transmitted non- A, non-B hepatitis – Mexico. MMWR Morb Mortal Wkly Rep 1987;36:597–602. 9 Valazquez O, Stetler HC, Avila C et al. Epidemic transmission of enterically transmitted non-A, non-B hepatitis in Mexico, 1986–1987. JAMA 1990;263:3281–5. 10 Arankalle VA, Chobe LP, Jha J et al. Aetiology of acute sporadic non-A, non-B viral hepatitis in India. J Med Virol 1993;40:121– 5. 11 Khuroo MS, Rustgi VK, Dawson GJ et al. Spectrum of hepatitis E virus infection in India. J Med Virol 1994;43:281–6. 12 Khuroo MS, Deurmeyer W, Zargar SA, Ahanger MA, Shah MA. Acute sporadic non-A, non-B, hepatitis in India. Am J Epi- demiol 1983;118:360–4. 13 Khuroo MS, Kamili S. Aetiology and prognostic factors in acute liver failure in India. J Viral Hepat 2003;10:224–31. 14 Khuroo MS, Kamili S. Aetiology, clinical course and outcome of sporadic acute viral hepatitis in pregnancy. J Viral Hepat 2003;10:61–9. 15 Kane MA, Bradley DW, Shrestha SM et al. Epidemic non-A, non- B hepatitis in Nepal: recovery of a possible etiologic agent and transmission studies in marmosets. JAMA 1984;252:3140–5. 16 Corwin A, Jarot K, Lubis I et al. Two years’ investigation of epidemic hepatitis E virus transmission in West Kalimantan (Borneo), Indonesia. Trans R Soc Trop Med Hyg 1995;89:262–5. 17 Corwin AL, Tien NT, Bounlu K et al. The unique riverine ecol- ogy of hepatitis E virus transmission in South-East Asia. Trans R Soc Trop Med Hyg 1999;93:255–60. 18 Aggarwal R, Naik SR. Hepatitis E: intrafamilial transmission versus waterborne spread. J Hepatol 1994;21:718–23. 19 Somani SK, Aggarwal R, Naik SR, Srivastava S, Naik S. A serological study of intrafamilial spread from patients with sporadic hepatitis E virus infection. J Viral Hepat 2003;10:446– 9. 20 Myint H, Soe MM, Khin T, Myint TM, Tin KM. A clinical and epidemiological study of an epidemic of non-A, non-B hepati- tis in Rangoon. Am J Trop Med Hyg 1985;34:1183–9. 21 Villarejos VM, Serra J, Anderson-Visona K, Mosley JW. Hepati- tis A virus infection in households. Am J Epidemiol 1982;115:577– 86. 22 Robson SC, Adams S, Brink N, Woodruff B, Bradley D. Hospi- tal outbreak of hepatitis E. Lancet 1992;339:1424–5. 23 Khuroo MS, Kamili S, Jameel S. Vertical transmission of hepa- titis E virus. Lancet 1995;345:1025–6. 24 Tsarev SA, Tsareva TS, Emerson SU et al. Experimental hepati- tis E in pregnant rhesus monkeys: failure to transmit hepatitis E virus (HEV) to offspring and evidence of naturally acquired antibodies to HEV. J Infect Dis 1995;172:31–7. 25 Psichogiou M, Tzala E, Boletis J et al. Hepatitis E virus infec- tion in individuals at high risk of transmission of non-A, non-B hepatitis and sexually transmitted diseases. Scand J Infect Dis 1996;28:443–5. 26 Khuroo MS, Kamili S, Yattoo GN. Hepatitis E virus infection may be transmitted through blood transfusions in an endemic area. J Gastroenterol Hepatol 2004:19:778–84. 27 Tsega E, Hansson BG, Krawczynski K, Nordenfelt E. Acute sporadic viral hepatitis in Ethiopia: causes, risk factors, and effects on pregnancy. Clin Infect Dis 1992;14:961–5. 28 Khuroo MS, Teli MR, Skidmore S, Sofi MA, Khuroo MI. Inci- dence and severity of viral hepatitis in pregnancy. Am J Med 1981;70:252–5. 29 Pina S, Buti M, Cotrina M, Piella J, Girones R. HEV identifi ed in serum from humans with acute hepatitis and in sewage of animal origin in Spain. J Hepatol 2000;33:826–33. Figure 41.2 Pathogenetic events in hepatitis E virus infection. HEV RNA in serum ALT HEV RNA in stool HEVAg in the liver IgG anti-HEV IgM anti-HEV 012345 Months post-infection Acute Convalescent phase 1405130059_4_041.indd 6311405130059_4_041.indd 631 30/03/2005 12:44:3230/03/2005 12:44:32 Chapter 41632 30 Tassopoulos NC, Krawczynski K, Hatzakis A et al. Case report: role of hepatitis E virus in the etiology of community-acquired non-A, non-B hepatitis in Greece. J Med Virol 1994;42:124–8. 31 Thomas DL, Mahley RW, Badur S, Palaoglu KE, Quinn TC. Epidemiology of hepatitis E virus infection in Turkey. Lancet 1993;341:1561–2. 32 Worm HC, Schlauder GG, Wurzer H, Mushahwar IK. Iden- tifi cation of a novel variant of hepatitis E virus in Austria: sequence, phylogenetic and serological analysis. J Gen Virol 2000;81(Pt 12):2885–90. 33 Zanetti AR, Schlauder GG, Romano L et al. Identifi cation of a novel variant of hepatitis E virus in Italy. J Med Virol 1999;57:356–60. 34 Hsieh SY, Yang PY, Ho YP, Chu CM, Liaw YF. Identifi cation of a novel strain of hepatitis E virus responsible for sporadic acute hepatitis in Taiwan. J Med Virol 1998;55:300–4. 35 Lok AS, Kwan WK, Moeckli R et al. Seroepidemiological sur- vey of hepatitis E in Hong Kong by recombinant-based en- zyme immunoassays. Lancet 1992;340:1205–8. 36 Mizuo H, Suzuki K, Takikawa Y et al. Polyphyletic strains of hepatitis E virus are responsible for sporadic cases of acute hepatitis in Japan. J Clin Microbiol 2002;40:3209–18. 37 Schlauder GG, Frider B, Sookoian S, Castano GC, Mushahwar IK. Identifi cation of 2 novel isolates of hepatitis E virus in Ar- gentina. J Infect Dis 2000;182:294–7. 38 Coursaget P, Leboulleux D, Gharbi Y et al. Etiology of acute sporadic hepatitis in adults in Senegal and Tunisia. Scand J In- fect Dis 1995;27:9–11. 39 Hyams KC, McCarthy MC, Kaur M et al. Acute sporadic hepati- tis E in children living in Cairo, Egypt. J Med Virol 1992;37:274– 7. 40 Centers for Disease Control and Prevention. Hepatitis E among U.S. travelers, 1989–1992. MMWR Morb Mortal Wkly Rep 1993;42:1–4. 41 De Cock KM, Bradley DW, Sandford NL, Govindarajan S, Maynard JE, Redekar AG. Epidemic non-A, non-B hepatitis in patients from Pakistan. Ann Intern Med 1987;106:227–30. 42 Erker JC, Desai SM, Schlauder GG, Dawson GJ, Mushahwar IK. A hepatitis E virus variant from the United States: molecular characterization and transmission in cynomolgus macaques. J Gen Virol 1999;80:681–90. 43 Kwo PY, Schlauder GG, Carpenter HA et al. Acute hepatitis E by a new isolate acquired in the United States. Mayo Clin Proc 1997;72:1133–6. 44 Schlauder GG, Dawson GJ, Erker JC et al. The sequence and phylogenetic analysis of a novel hepatitis E virus isolated from a patient with acute hepatitis reported in the United States. J Gen Virol 1998;79:447–56. 45 Tei S, Kitajima N, Takahashi K, Mishiro S. Zoonotic transmis- sion of hepatitis E virus from deer to human beings. Lancet 2003;362:371–3. 46 Arankalle VA, Paranjape S, Emerson SU, Purcell RH, Walimbe AM. Phylogenetic analysis of hepatitis E virus isolates from India (1976–1993). J Gen Virol 1999;80:1691–700. 47 Tsarev SA, Binn LN, Gomatos PJ et al. Phylogenetic analysis of hepatitis E virus isolates from Egypt. J Med Virol 1999;57:68–74. 48 Wang Y, Zhang H, Ling R, Li H, Harrison TJ. The complete sequence of hepatitis E virus genotype 4 reveals an alternative strategy for translation of open reading frames 2 and 3. J Gen Virol 2000;81(Pt 7):1675–86. 49 Tsarev SA, Shrestha MP, He J et al. Naturally acquired hepatitis E virus (HEV) infection in Nepalese rodents. Am J Trop Med Hyg 1998;59:242. 50 Haqshenas G, Shivaprasad HL, Woolcock PR, Read DH, Meng XJ. Genetic identifi cation and characterization of a novel virus related to human hepatitis E virus from chickens with hepa- titis-splenomegaly syndrome in the United States. J Gen Virol 2001;82:2449–62. 51 Aggarwal R, McCaustland KA, Dilawari JB, Sinha SD, Rob- ertson BH. Genetic variability of hepatitis E virus within and between three epidemics in India. Virus Res 1999;59:35–48. 52 Labrique AB, Thomas DL, Stoszek SK, Nelson KE. Hepatitis E: an emerging infectious disease. Epidemiol Rev 1999;21:162–79. 53 Arankalle VA, Tsarev SA, Chadha MS et al. Age-specifi c preva- lence of antibodies to hepatitis A and E viruses in Pune, India, 1982 and 1992. J Infect Dis 1995;171:447–50. 54 Paul DA, Knigge MF, Ritter A et al. Determination of hepatitis E virus seroprevalence by using recombinant fusion proteins and synthetic peptides. J Infect Dis 1994;169:801–6. 55 Aggarwal R, Shahi H, Naik S, Yachha SK, Naik SR. Evidence in favour of high infection rate with hepatitis E virus among young children in India. J Hepatol 1997;26:1425–6. 56 Dawson GJ, Chau KH, Cabal CM, Yarbough PO, Reyes GR, Mushahwar IK. Solid-phase enzyme-linked immunosorbent assay for hepatitis E virus IgG and IgM antibodies utilizing recombinant antigens and synthetic peptides. J Virol Methods 1992;38:175–86. 57 Zanetti AR, Dawson GJ. Hepatitis type E in Italy: a seroepi- demiological survey. Study Group of Hepatitis E. J Med Virol 1994;42:318–20. 58 Mast EE, Alter MJ, Holland PV, Purcell RH. Evaluation of assays for antibody to hepatitis E virus by a serum panel. Hepatitis E Virus Antibody Serum Panel Evaluation Group. Hepatology 1998;27:857–61. 59 Mast EE, Kuramoto IK, Favorov MO et al. Prevalence of and risk factors for antibody to hepatitis E virus seroreactiv- ity among blood donors in Northern California. J Infect Dis 1997;176:34–40. 60 Nanda SK, Ansari IH, Acharya SK, Jameel S, Panda SK. Pro- tracted viremia during acute sporadic hepatitis E virus infec- tion. Gastroenterology 1995;108:225–30. 61 Aggarwal R, Kini D, Sofat S, Naik SR, Krawczynski K. Dura- tion of viraemia and faecal viral excretion in acute hepatitis E. Lancet 2000;356:1081–2. 62 Aggarwal R, Kamili S, Spelbring J, Krawczynski K. Experi- mental studies on subclinical hepatitis E virus infection in cy- nomolgus macaques. J Infect Dis 2001;184:1380–5. 63 Melnick JL. Enteroviruses: polioviruses, coxsackieviruses, echoviruses, and newer enteroviruses. In: Fields BN, Knipe DM, Howley PM, eds. Fields Virology. Philadelphia: Lippin- cott-Raven, 1996:655–712. 64 Arankalle VA, Joshi MV, Kulkarni AM et al. Prevalence of anti- hepatitis E virus antibodies in different Indian animal species. J Viral Hepat 2001;8:223–7. 65 Chandler JD, Riddell MA, Li F, Love RJ, Anderson DA. Sero- logical evidence for swine hepatitis E virus infection in Aus- tralian pig herds. Vet Microbiol 1999;68:95–105. 66 Clayson ET, Innis BL, Myint KS et al. Detection of hepatitis E virus infections among domestic swine in the Kathmandu Val- ley of Nepal. Am J Trop Med Hyg 1995;53:228–32. 1405130059_4_041.indd 6321405130059_4_041.indd 632 30/03/2005 12:44:3230/03/2005 12:44:32 [...]... Symposium on Viral Hepatitis and Liver Disease, London, May, 1 987 In: Zuckerman A, ed Viral Hepatitis and Liver Disease New York: Alan R Liss,1 988 :131– 7 8 Reyes GR, Purdy MA, Kim JP et al Isolation of a cDNA from the virus responsible for enterically transmitted non-A, non-B hepatitis Science 1990;247:1335–9 9 Zuckerman AJ Twenty-five centuries of viral hepatitis Perspectives in viral hepatitis Rush-Presbyterian-St... (n = 330) 1972–1 984 India2 08 (n = 4 58) 1992–19 98 India13 (n = 423) 1 987 –1993 Japan209 (n = 236) 1 983 –1 987 Hepatitis A virus Hepatitis B virus Hepatitis E virus Acetaminophen Drug Indeterminate 5 9 0 54 7 17 . epidemic of non-A, non-B hepatitis: possibility of another human hepatitis virus distinct from post- transfusion non-A, non-B type. Am J Med 1 980 ; 68: 8 18 23. 2 Vishwanathan R. Infectious hepatitis. signs Delhi, India 80 1956 (%) (n = 9 58) Accra, Ghana 78 1963 (%) (n = 136) Kashmir, India 1 19 78 (%) (n = 275) Ethiopia 79 1 989 (%) (n = 423) Xinjing, China 81 1 986 88 (%) (n = 85 ) Jaundice 100. enterically transmitted non-A, non-B hepatitis in Mexico, 1 986 –1 987 . JAMA 1990;263:3 281 –5. 10 Arankalle VA, Chobe LP, Jha J et al. Aetiology of acute sporadic non-A, non-B viral hepatitis in India.